I have questions about repeating sins. I clearly know that being in a haram relationship is wrong and awful and I keep asking forgiveness from Allah swt and I pray for Him to protect me from the whispers of shaytaan. But why do I keep repeating the same sins over & over again. I am always sad whenever I do it but I feel like I fell deep down and He won’t forgive me. Please help me.
The reason is that avoiding sin requires feeling deep sense of loyalty toward God. It is not sufficient to merely acknowledge in your mind that God exists and that sins are wrong. You need to make His presence feel real to you, and that requires daily work.
Trying to avoid repeating sins is similar to trying to lose weight by eating less when your house is filled with delicious things like cake and ice cream. Today you might watch a very inspiring lecture or short film that motivates you to lose weight so that you avoid eating the foods you like. But tomorrow, your motivation will have evaporated, and unless you do the necessary work to feel motivated again, you will likely start eating those foods again.
It is in human nature to be attracted toward certain sinful things. Unless we work every day to keep our motivation for avoiding sins, our human nature reasserts itself so that we end up engaging in those sins. What I recommend is to perform at least an hour of tahajjud and Quran reading before bed (see here for the details). If you maintain that just for a week, you will likely be able to effortlessly avoid all sins because you will feel close to God and loyal to Him throughout your day so that it feels out of character to sin.
However, if you start doing that and it helps you avoid repeating sins, if stop doing it then you will again start sinning. If you are truly intent on avoiding sins, you have to make the decision to spend a certain amount of time every single day in extra worship for the rest of your life. There are no short-cuts, no permanent solutions. It is a daily challenge and we have to meet it every single day if we want to remain spiritual and pure of sin.