We all seek happiness and have a need for it. Each one of us has a definition for happiness and has some idea as how to achieve it. It is my pleasure to present for you in this article what I regard as the ultimate recipe for happiness, based on the Holy Quran and the teaching of Prophet Muhammad (God's blessings and peace be upon Him).
Make it a conviction that there would never be a wide and continuous happiness and tranquility unless you love God and His Prophet more than anything else.
Anas bin Malik (May Allah be pleased with him) reported that Prophet Muhammad (God's blessings and peace be upon Him) said:
"There are three qualities whoever has them, will taste the delight of Belief (Iman): To love Allah and His Messenger (God's blessings and peace be upon Him) more than anyone else; to love a servant (of Allah) only for (the sake of) Allah; and to abhor returning to infidelity after Allah has saved him from it as he would abhor to be thrown into the fire (of Hell)"
[resource: Al-Bukhari and Muslim].
Based on this, tranquility and inner peace are a direct result of God's obedience, good doings and avoidance of sin. After God had expelled Adam & Eve from heaven and after He had previously warned them against Satan, He said to them:
(123) "Get you down (from the Paradise to the earth), both of you, together, some of you are an enemy to some others. Then if there comes to you guidance from Me, then whoever follows My Guidance shall neither go astray, nor fall into distress and misery." (124) "But whosoever turns away from My Reminder (i.e. neither believes in this Qur'ân nor acts on its orders, etc.) verily, for him is a life of hardship, and We shall raise him up blind on the Day of Resurrection."
[Surat T.H. / The Holy Quran]
Keep in mind that God's obedience brings calm to the heart, takes away worry and that sin withholds and disturbs tranquility. The more you are delighted in God, the highest God will value you. Gods Contentment upon you secures His guidance, protection, continuous peace and spiritual supply. People close to God describe that inner peace as more valuable than all earthily possessions. This matter is evident in the following Qudsi Prophet Saying where God describes that which He would provide His true servants with:
On the authority of Abu Hurayrah (may Allah be pleased with him), who said that the Messenger of Allah (God's blessings and peace be upon Him) said:
"Allah (mighty and sublime be He) said: Whosoever shows enmity to someone devoted to Me, I shall be at war with him. My servant draws not near to Me with anything more loved by Me than the religious duties I have enjoined upon him, and My servant continues to draw near to Me with supererogatory works so that I shall love him. When I love him I am his hearing with which he hears, his seeing with which he sees, his hand with which he strikes and his foot with which he walks. Were he to ask [something] of Me, I would surely give it to him, and were he to ask Me for refuge, I would surely grant him it. I do not hesitate about anything as much as I hesitate about [seizing] the soul of My faithful servant: he hates death and I hate hurting him."
If Satan mislead you and made you commit a sin then know that Allah loves the repentant. So all you have to do is to ask Him for forgiveness. Know that regretting doing a sin ensures atonement (i.e. true regret due to fear of God). Recall always God's name "The Forgiver" (الغفور). If we were not sinners then God would had not asked us to ask Him for forgiveness.
Accordingly, happiness and tranquilly can be found in the close relationship between Man and the Creator; in the spiritual supply and light that God blesses His true servants with. Moreover, the good can be obtained directly in the beneficial outcomes of God's obedience i.e. in following His guidelines and avoiding sin. No one of us can deny the refreshing benefits of Ablution (Wudu), especially when done using cold water. The process energizes the body and improves blood circulation. Likewise, no one can deny the mutual benefits of kindness, of a nice word and calm voice. Fasting and its spiritual benefits are also evident for every believer. If you had been too lazy one day to wake up and pray the Fajr in time, then you know surely the negative impact of that on the whole day (laziness, passiveness, sad mood etc..). So, the true knowledge and all the solutions are available in the Book of God and in the teachings of His Prophet (God's blessings and peace be upon Him). God says in Surat Al Naml describing the Holy Quran:
"And it is certainly guidance and a mercy to the faithful."
[Surat Al Naml / The Holy Quran]
Make sure to read in the Holy Quran on a daily basis. In it the reminder and the true generous promise. Reading it lets God's mercy and tranquility fall upon your heart and home. Prophet Muhammad (God's blessings and peace be upon Him) said:
"Do not turn your houses into graveyards. Satan runs away from the house in which Surat Al-Baqarah is recited."
[Reported by Abu Hurairah (May Allah be pleased with him) / Sahih Muslim]
My Brother! Go to the Mosque and make the prayer there. My Sister! Pray on time at your home. Pray the Fard (obligatory prayer) at the Mosque and pray the Nafelah (Voluntary Prayer) usually at home, since doing so is a Sunnah.
Arrange your daily tasks and obligations around the 5 prayer times. In this manner, you will not miss a prayer at the Mosque and you shall not be deprived of God's full care and mercy. Do that which God loves and God should give you the desires of your heart.
Keep remembering God all the time. This includes remembering Him using the sayings Prophet Muhammad (God's blessings and peace be upon Him) had taught us e.g. upon waking up in the morning, when dining, when leaving the home, upon entering it and all other prayers (maybe link here to prayers in English). Moreover, remember God always in your heart in form of Tahlil (saying "There is not God but Allah"), Tasbeh (saying "Glorified Allah"), Tahmeed (saying "Thanks to Allah"), Takbeer (saying "Allah is the Greatest"), asking Him for forgiveness, Salat upon the Prophet (God's blessings and peace be upon Him). Prophet Muhammad (God's blessings and peace be upon Him) said:
"When you get up in the morning, charity is due from every one of your joints. There is charity in every ascription of glory to Allah; there is charity in every declaration of His Greatness; there is charity in every utterance of praise of Him; there is charity in every declaration that He is the only true God (worthy of worship); there is charity in enjoining good; there is charity in forbidding evil. Two Rak'ah of Duha (Forenoon prayer) is equal to all this (in reward)"
[Reporetd by Abu Dharr (May Allah be pleased with him) / Muslim]
Finally, I encourage you to reflect upon this great saying of Prophet Muhammad (God's blessings and peace be upon Him):
"Whoever makes the Hereafter his goal, Allah makes his heart rich, and organizes his affairs, and the world comes to him whether it want to or not. And whoever makes the world his goal, Allah puts his poverty right before his eyes, and disorganizes his affairs, and the world does not come to him, except what has been decreed for him."
[Reported by Anas bin Malik / Jami` at-Tirmidhi].
The winner is the one whose supreme goal is God and the Day of Judgment.
Those were some points I wanted to present here. They are important building blocks for success and prosperity in this life and in the Hereafter. Make a consideration as to where you stand in relation to them, and make any necessary modifications. Do and rely on Allah and be reassured that God would reward you for all good that you do, small or big.