Readiness, trying, courage and learned helplessness

When is the right time to make an effort? I read a lot of advice about "don't wait until you're ready, do it now".

I have tried to do a thing dozens, possible over a hundred times. Each failure is demoralising. In spite of that, some days I feel like trying again and I do (and I fail). And some days, I know I can't do it.

I feel like the accumulated weight of failure is making it harder and harder over time, and if I try on the days when my energy and hope is lowest, I will only cement that demoralisation.

What would you do?