This may be a little vague. Nonspecific advice.
To keep at it (I hope this doesn't sound completely useless), you just have to, well, keep at it. The more you practice interacting with others, the easier each interaction becomes. Eventually, you notice that you can handle far more than before, before you need to retreat into your own space. And you may just have to accept that, even at your best, you can't handle as much as the average person. There's nothing wrong with being less social than most people, as long as you are able to find a balance that makes you happy and allows you to achieve your goals.
As for not annoying people, I've found that people seem to like me if I follow three basic rules:
1. Talk less than the other person.
2. At least half of what you say should be questions, either about themselves, or about some topic they fancy themselves experts on.
3. When in doubt, shut up.
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If life's not beautiful without the pain,
well I'd just rather never ever even see beauty again.
Well as life gets longer, awful feels softer.
And it feels pretty soft to me.
Modest Mouse - The View