So much good advice here! I like the idea of not locating (all) your self-confidence in your past. That said, it does help sometimes to look back at something and say “well, I was terrified and I did that and it did/didn’t work out, but I made it through, so I can do something new again…”
The more you do stuff that scares you, the more that you put yourself out there, the easier it gets to do so. I don’t mean that you stop feeling scared of failure, having serious bouts of self-doubt, or hearing a string of horrible “what ifs” in your head. I mean that it gets easier to have those and not let them stop you.
Also, a good way to get self-confidence is to fail. Fail, fail, fail, fail. Don’t be afraid to fail. It’s pithy to say “you learn more from failure than success.” (I’d volunteer to try out never failing again no matter what I tried, to test this theory.) In failing you learn it isn’t the end of the world to fail. You learn that you can get up again. You learn that sometimes you’re not very good at something and either need to work to get better or do something different. This is the major element I see lacking in my students (college age). They haven’t failed a lot, so they don’t know how. And of course lack of knowledge is terrifying. Failure has been built up as “not an option” (oh, it’s ALWAYS an option — just not the one we’d prefer), when what they need is to fail and get over it.
When I was a kid, about 6 or 7 (maybe younger), I knew how to swim (my mom first took me in the pool at age 6 months). I didn’t know how to swim in the ocean, and my folks were big beach people. So we went to the beach, and my dad took me out into the ocean with a boogie-board. When the right big wave came (it looked huge to me, but it probably wasn’t), my dad let me go. It did not go well. I got turned sideways, fell of, and tumbled over and over as the waves shoved me toward shore. I finally got my footing, stood up, and was hacking and coughing and starting to cry. On shore, my parents were cheering for me — especially my mother. I remember thinking “well, okay then, I guess it wasn’t that bad…” and I was never afraid of the ocean again. I’m pretty sure my parents let me fail miserably on purpose. This is one example, but my parents were pretty big into this kind of teaching. They encouraged me to do things (sometimes whether I wanted to or not) and it was fine to fail. I don’t know that I’ve got the confidence in my abilities that I want (who does? besides perhaps our current president), but I know I can do/try things anyway.