Momentum makes confidence less theoretical.

Confidence assembled from encouragement is thin, because underneath you know it rests on nothing you have done. Confidence built from a record of actually turning up and doing the thing is different, since it is a conclusion drawn from evidence rather than a mood you are maintaining. That is why doing the work reliably changes how you feel far more than any amount of reassurance.

If you are waiting to feel ready, work on the evidence instead. Accumulate a few weeks of showing up. The feeling generally follows the record rather than the other way round.