How and when should we supplicate? What are the most grateful supplications?

"I had a relationship with a boy I thought would be my husband. Unfortunately we broke up and he married someone else closely after us. I know that all types of relationships between man and women that are not related are haraam. And I really regret having the relationship and I am afraid of Allahs punishement. I didn't have intercorse with that boy el hamdullilah but I did kiss him. I seek everyday forgiveness and I wonder if Allah will forgive me?

Dear Brother / Sister,

Man’s creation is suitable both for good deed and sin. So, he, time to time, may commit sin willingly or unwillingly. On this matter in the Qur’an it is said: “Allah forgives not that partners should be set up with Him; but He forgives anything else, to whom He pleases; to set up partners with Allah is to devise a sin most heinous indeed.” (An-Nisaa, 4/48-116). With these verses it is expressed that whatever sin committed may be forgiven except setting up partners with Allah.
In our books it is expressed that the repentance made with heart and soul will be accepted by Allah. Thus, Allah, the most Compassionate, with the verse “O you who believe! Turn to Allah with sincere repentance: in the hope that your Lord will remove from you your evil deeds and admit you to Gardens beneath which Rivers flow …” (At-Tahrim, 66-8) declares that the repentances made will be accepted. The sincere repentance mentioned in the verse is as follow:
1.    Being aware of the committed sin before Allah and due to that sin, taking refuge in Him and feeling sorry.
2.    Feeling sorry for the sin committed and conscientiously being uncomfortable because committing such a sin before the Creator.
3.    Being in a determination of not committing such a sin any more.
4.    If it is concerning with rightful share, forgiving each other.

In one Hadith Our Prophet said as follow: “Sincere repentance is this:
-Regretting for the sins.
-Performing obligatory worships.
-Not doing cruelty and hostility.
-Making peace with hurt and cross.
-Being in determination of not going back to sin any more.”
Inshaallah if these conditions are applied, we hope that Allah will accept our repentances.
However, man, every time, should be in a feeling between hope and fear. Neither we may rely on our worships, nor fall into despair due to our sins. As for it is wrong to say “I am very good, I managed that work.”, so too, saying that ‘Allah will not accept me’ is wrong at the same degree.
How and when should we supplicate? What are the most grateful supplications?

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