But what if I simply mess it up in the moments when I should resist?
This is the problem. In these deciding moments I mess it up. I don't even try to resist. Sometimes I do and fail but many times I don't even have much resistance. And then later I think how am I even able to sin, how can I suppress the feeling of guilt for this time? Nobody would steal if he knew that he is being watched, but I can sin even though I know God knows it, how is this possible?
But I really don't know HOW to have victory. I have tried to gear up my will, it didn't work very long. As soon as I get depressed or frustrated I fail. Or when my relationship with God is disturbed then I also sin much easier because I feel like it doesn't matter anyway because my relationship is already so bad.
I have searched help from some christians and asked how exactly I become free but they couldn't really help me. No matter what I do is wrong. If I gear up my will I fail and also christians will say that you cannot win this way anyway. But if I don't try to resist then it's also wrong. So what shall I do?`I have prayed and I have wanted to finally change something so often but I fail time and time again and I don't even have faith in myself anymore, how can I have faith that it'll ever change when I fail all the time?
I thought resisting is important but then I read a book which said if you try to fight sin in your own strength you are bringing strange fire to God.
Great! This means no matter what I do is wrong. I also think that I might be addicted to some sins. I read that sinning can release neurotransmitters which make you happy and once you're addicted to this then it'll repeat itself again and again.
And does this mean that if I do not get rid of habitual sins I'll go to hell?

Because christians say that a real christian cannot sin habitually. But if he cannot do this then how often does a real christian sin? like once every week or once every months?