You're literally "made to feel" certain ways. During your formative years someone was shouting you suck and generally acting as you're a burden and unwanted? You'll feel that shit for the rest of your life no matter what you "decide to think". It becomes ingrained in you. It becomes who you are. You can work on it like GP said and improve the situation but don't act like it's trivial or just a change of perspective. It isn't. It's like your body needs healing after a fractured bone. Your mind also needs that time and setting.