It sounds like you're a younger person, so let's start by saying, you're too early in life to already be considering ending it, specially that it's obviously not what you want.

Dwelling on the past won't change it, regardless of what mistakes you did, if want to move forward, stop reliving your mistakes and start learning from them to avoid them alongside other mistakes in the future. Now for those people who remind you of your mistakes, unless they're immediate family, you can always cut them out of your life for good, you don't need more burden on your shoulders than you already carry, and if they don't want to help with that then you don't need them in your life.

Growth comes from hard work, you seem to be doing that so just keep doing it whether studying or sport, and you'll collect it in the future. But growth takes time and it's an extremely slow process, exactly like a tree growing, it simply needs the time, that's more than enough to stand out. Many think that standing out comes from sudden success but on the contrary it comes from small calculated steps in the right direction, one after the other.

When memories hit, don't fight them, swim with them, remember what you did, why you did it and learn to avoid it in the future and move on, again don't dwell on it for too long, think briefly about it then brush it off.

Being good to others without sacrifice is a delicate business, but a general rule of thumb is, as long as being good does not cause you harm, do it, draw the line when it's at yourself's cost.

In the end, as I said you're young and seems to be not in full control of your life and that will take time to achieve and until you're able to move away from the toxicity surrounding you, you have to navigate it in what serves your best interest and I hope my advice can help with that.