This is still a challenge for me at times. I think the best thing to do is allow your mind to observe without getting attached to such things in inner dialogue. The more you practice this, the more natural it's going to become. I think positive reafirmations and mantras also combat this issue very well.
Through self-compassion. Negative thoughts have plagued me for most of my life until last year, when I started Cognitive Behavioural Therapy and meditation. Be mindful of these thoughts and stop when one crops up. Perhaps write it down for greater clarity. Reframe it in a way that takes into account that you did your best and that whatever happened doesn't reflect on you and your worth. Deconstruct it. After thinking " I really screwed that up. Why am I so clumsy?" you should challenge this thought and say, " Actually I did what I thought was best in that situation. I tried to be kind/ perceptive/ helpful. My intentions were good, even if the outcome wasn't perfect." Apologise if you need to, and learn from your mistakes. But don't pile criticism upon yourself that you wouldn't dish onto others. Good luck! You're worth it.
I am currently using theta wave and positive affirmation meditation to help reprogram my mind to think more positively. I also challenge negative thoughts by reframing them.
I don’t think having negative thoughts is a bad thing; it’s normal. The key is to acknowledge them and accept that you feel them. In doing so, you feel at peace with your emotions. Therefore, your inner mind has returned to normal and you feel better again!