I know you might be going through a rough time right now and I definitely get where you're coming from since I have 2 older sisters, 1 was considered the prettiest and the other was considered the smartest and they would get compliments on these respective areas a lot to the point where it felt like I was neither smart nor pretty so I wasn't good at anything etc. But, I learnt that I shouldn't compare myself to them even if they get more compliments or whatever and I get none (except the occasional pity compliments) because there's always going to be someone better and there's always going to be people saying things about you instead you should have your own sense of self, make your own new standards and live up to them and love yourself for living up to them. However, I know it can be hard to do this at first so try first of all just incorporating the phrase 'good enough' into your life. For example, I would tell myself well I'm not as smart or pretty as my sisters but I'm good enough. Sorry I know my grammar was terrible but hope this helps