When you keep thinking on the past

I don't think you're sinning as such, but it does seem to be a bondage. Making yourself feel guilty about it doesn't change anything. It's like making yourself smile when you're in pain. It doesn't make the pain go away, but you can sometimes fool yourself into thinking that you feel better. The better way to deal with it is to pray about it and simply ask God to help you see what you need to know to get through it. Then trust Him to lead you, and He will. He doesn't want you to hurt; He wants to heal your mind of all the bad things that have happened. These things don't heal with just a band aid, they need surgery, and God can do that.

It is not good to focus on the past. As you said, you bind yourself to the past and you fail to enjoy the present. The past is just that, past. Nothing you do now will change. Accept it, learn from it. See what it mad eyou now and keep the reference in your mind for future like situations so that you know how you want to act next time. But do not tie yourself to something you can do nothing about.

I'm not sure it would be considered sinning, but it does keep you from making any spiritual progress to keep looking at what you did or didn't do in the past. It does tend to bog you down! Keeping your focus on God all the time is always good advice. That is where we can receive peace and grace and guidance. It's when we try to do everything by ourselves that we make the biggest messes! LOL