First of all, figure out what's "good for you" versus what's a societal expectation that you can skip. For instance, when I was younger, I didn't like going clubbing or taking dates to loud bars with groups of people, because that's...not me. Solution: go for coffee/lunch dates instead. Easy.
For things that are "good for you" but not comfortable, find ways to make them easier based on your known preferences. As an example, I decided that I wanted to go to some networking events. While there, I tried to talk to other people who were there by themselves; it was easier for me to strike up at 1:1 conversation than to try to join a big group. I also found that if I went to networking events alone, not with a friend, it was easier to meet people.
Your preferences may be different, but play to your strengths or the things you already know you can do, and build from there.