In 2009 I had two portrait commissions in a row go wrong. In the first one I allowed time pressure to get the better of me and I let the painting leave with a less-than-acceptable likeness. My fault. In the second one, the client sent me a - literally - postage-stamp sized reference, and then got angry when I couldn't get a good likeness. The combination of the two, at a time when I had a LOT of other pressures in my life, put me right off portraiture (and, frankly, people in general).
In the years that followed I'd look back at my early (successful) portraits and think, I couldn't paint like that now if my life depended on it. I've forgotten how, I've filled my head with theory instead of just painting (to the point where I'd try to paint, and all I could think of was all the theories and "rules" I was supposed to be adhering to, meaning I ended up with very tight paintings that I didn't enjoy doing).
This year I decided it was time to confront the fear - and I use that word quite deliberately - head-on (pun intended!). I asked my Instagram friends for a volunteer to have their portrait painted, and one did. The first attempt at her painting was abandoned when the likeness slipped away and it was obvious it would be less work to start again than it would to correct what I'd done. The second attempt came out great:

Now I'm working on a nude (based on a photo by ~
chamberstock) that I've wanted to paint for years, and it too is coming along very well so far:

I guess the lesson is, it's better to just try than to listen to doubts (yours, or anyone else's). Whatever happens, you end up finding out what's real, and what's just fear or doubt. I wish I'd done it years ago, because the simple truth is, I ***love*** painting portraits and nudes