Why do I keep trying and when will I stop?

I am not new to people making plans with me and then either backing out last minute or simply not showing up. It has happened so often that I am honestly surprised when someone actually keeps their plans. Often times I fight myself to not break plans before someone else does, because if I break the plans then I won't be hurt once again and my trust won't be broken, once again. 

In conversations with people about friendship and trust, I always think and at times end up saying "I don't trust anyone". When asked "Why?" I answer because I have spent a lot of years being given reasons to not trust people, followed by examples. 

At work I trust, for the most part, because that involves a small group of people who all have the same goals for eight hours. 

Outside of work, in my personal life, I have very little trust in pretty much everyone because I've been let down to many times. 

Why do I decide to keep trying, when it ends up bad?

     I keep telling myself "It'll be different this time"

Why do people do this? 

    Very good question and I will probably never get an answer

Why do people not respond to messages to set up or confirm plans? 

    I suspect they don't want to hurt my feelings by canceling. However, not responding is a VERY LOUD RESPONSE and hurts A LOT more than just canceling

Why is it so hard to say "I've changed my mind" or "I don't want to go"

    Another good question and I will probably never get an answer

Why does this happen to me, all the time?

    Good question. I am not sure

Why do I keep trying? 

    Because I am stupid in thinking that people will change

When will I stop?

    I'm thinking now is a good time. 

I constantly worry when I do make plans, that they will cancel at the last minute. I've worked hard to message every so often but not so much that I seem needy. If I get no response after a couple messages, then I am done trying, I won't keep trying after that, it gives me time to come to terms with being canceled on again, through ghosting.

Because I end up doing so much on my own anyway, it's probably best to just keep it that way. People have proven time and time again that they will not follow through for whatever reason. My upcoming plans will happen with just me and as much as I don't like it, it's just how it is. It's one more person to not trust and I won't ask again.