It surprises me how people critique themselves so harshly; I can be one of those. We should be our own biggest fans! But in a society that pushes a view that you aren't enough until you buy this or achieve that, it's hard to celebrate ourselves, and it's easy to see and dwell on our glaring faults and forget our good bits.
Sometimes it's not just ourselves doing the critiquing- sometimes it's others offering their judgements - on purpose to cause pain, or from a place of ignorance. No matter how the words come, they hurt the same. And it can be very easy to agree and take on these words as part of ourselves.
It doesn't matter what someone says to you when it's from a place of their own fear or insecurities. It's meaningless... because it's not true. If words spoken over you aren't edifying, then they aren't true and they don't reflect who you truly are.
If someone's opinion about you makes you feel ashamed, withdrawn, shut down, guilty or low, then it's not truth. And so you can instantly discard it, like water off a duck's back.
Because who you areis not a failure, or a fool, or only worthy of attracting bad partners, or ugly because of your weight or your nose or whatever! I don't know what refrains rattle around your brains, but everyone has some internal self-destructive mechanism that hinders self-acceptance and inner-peace! You know what it is. You know what words your mother said to you or your father, or your friend or your teacher or other half. The words that start out as teasing, but with repetition build up in your psyche and incorporate in to your self-image. Maybe for you, you didn't just suffer teasing and taunts, but verbal abuse, and that's a deeper trauma to recover but it's still recoverable.
Build a thick skin made from good positive words about yourself- every word of praise, every compliment, every recognition and acknowledgement. Record them, write them down and repeat them to yourself! Stick 'em up as post-its on your mirror!
And if you're racking your brains trying to think of one nice thing someone has said about you and can't, compliment yourself! And then compliment those around you, because when you start looking for positive in others, it's easier to see positive things in yourself and vice versa, and it will shift the dynamic of your friendships to be one of respect and building each other up.