Why is it that no matter how hard I try, I still can’t change myself for the better?

You have identified as yourself a part of yourself that believes you are not good enough and simultaneously tries to be good enough.

As long as you keep believing that you are not good enough, no matter what you do, you will carry the reality of being not good enough with you.

Trying to change externals without having the inner realization of your true nature will never give you lasting satisfaction.

Look at your life, change is always happening, you are not the same person as yesterday.. or last year. Some things have changed and are continually changing.

All that is needed to change yourself for the better is to realize your true self while change is happening in your life. Realizing your true self will make you feel happy and peaceful in the present moment, while change is happening. Therefore, you will experience ‘yourself’ happily changing.

You are not the content of your mind, you are not your emotions, you are not your body, you are not anything in existence. These are all happening within you. Realize yourself/live with this realization and your question will be satisfied.