How to get over the fact you messed up many opportunities for friendship by being slightly negative?

I“m male early 30’s.

I’m not a very social person. i’m shy. and I always think of my self as a piece of c*ap. Useless and stupid. etc.

but I’ve done the Craiglist thing and recently tried the facebook thing to try to meet people living locally. Also i’ve made some connections through the local College’s international student program where you can meet foreign students in America.

Well, i meet them through email and then we mail a few times, then I just say something a bit negative and they suddenly stop contacting me. I personally, don’t get it, maybe those people are too sensitive..

for example I was mailing this girl from japan studying in my city. She was happy and we were going to meet soon, then i sent an email saying “maybe you’re busy and you don’t need friends”
or
-“Yeah let’s meet but i’m afraid you’ll hate me because I’m not an outgoing party guy”

Just little comments like that that slipped out. Once you send the email you can’t take it back, so i guess i should’ve said that but well.. Anyways, or other times we’ll meet 1 time in real life, then i send a mesage

-“It was great. thanks for meeting with me but maybe I’m not good for you because I’m not an outgoing white guy. i’m a shy guy and i’m not a good speaker. so tell me if you don’t want to see me anymore”

Those comments don’t actually mean i don’t want to meet them but that that’s what i think because I’ve seen it over and over , i always see how most people at work and most foreigners are always really happy with party type personalities.

But anyway, recently this happened again and so the person that was going to be my friend, is no longer emailing me and it’s sad.
what to do?