How to develop a strong mindset or is it really a thing

Well i dont clearly know what i want to ask for but i know i have really strong values and a strong faith in Allah and i genuinely believe everything will work out for me but still i feel sad and helpless alot of the times i think its generally because i overthink alot and my thoughts get to me making me feel sad quite often and i kinda also suffer with self esteem issues like i start to believe i am not worthy of good things for some reason i think i became like this because of my rough childhood but i genuinely want to fix it i want to develop a strong mindset where i am not affected by unnecessary thoughts.