Flaking out

I have this thing that whenever I want to do something I doubt it's possible. I want to conquer it and be a better person it's not dependable to always be saying yes then saying no I'd like to be more sure of myself how do you do it?

I get this fear and then I chicken out and say I can't do it sometimes I put things off until last minute then I say there's not enough time and I don't go I don't do what I was going to do and it's like I talk myself out of it.

Sometimes I have events and I look through my closet and I can't decide what to wear and I take out my clothes closet looking for something to wear the other thing is I shop at the store and nothing looks good or nothing fits well and I decide I don't have something to wear to the event and I don't go.

I also sometimes want to go to events but then I say financially it's not worth it paying for the class or registration I talk myself out of it. I'm also shy insecure and I get scared about meeting new people and worry preoccupation if they will dislike me or look at me like I don't fit in. I get scared people who talk about me bully towards me laughing at me you know like oh look at what's she's wearing or stuff like that.

I'd like to be more secure sure of myself and I'd like to believe in myself how do you have more confidence in yourself and make sure you do what you say you will do be a person who is responsible.