A lot of history was made by people your age who didn’t feel ready either.

Readiness is mostly a feeling, and a poor predictor of capability. Plenty of people who changed something were young, frightened and visibly out of their depth while doing it, which is only invisible afterwards because the story gets told backwards from the result. Almost nobody waits for the nerves to clear, because for most worthwhile things they do not clear in advance.

Take the thing you have been putting off until you feel prepared and do the smallest real version of it this week. Send the message, enter the contest, ask the question. Prepared tends to arrive afterwards.