It is a common misconception that you either accept yourself or change because people think that acceptance means to do nothing. This is where you have people that believe if you accept their faults and weaknesses that means they should not changing their faults and weaknesses.
Acceptance does not mean not changing; acceptance leads to change. For example, the journey for addicts to combat their addiction begins with acceptance. When addicts seek help, the therapist does not congratulate them for acceptance, and instead encourages and helps the addicts change. Those who do not accept that they have a problem do not change.
Therefore, you should always accept yourself, and accept everything about yourself.
People often try to rewrite or change history in the past, but they were a different person in the past compared to now. So there is no point in looking back, holding guilt for past mistakes, and trying to change that past. Instead have self compassion toward your past self, acknowledging that blaming your past self does nothing, and then accept who you are in the present. You were never perfect before and you are not perfect now, but you can change, fix, and grow now.
You might feel there is no hope in changing because you have messed up so much. But those thoughts could be depression trying to convince you that your situation is worse than it actually is. This is because the human ability to accept and change also gives humans the ability to have depression. It was a major evolutionary change in the mind that helps preserve humans. Learning what you can trust from your mind is powerful, and knowing what thoughts to trust comes from meditation.