Sometimes you have to accept that your best isn’t good enough. Perhaps you’re losing clients, not meeting targets or not making enough to meet your basic needs like food and shelter.
But other times the case is that you aren’t actually offering your best, you’re giving half-heartedly.
It’s really just an excuse for fear of trying and fear of failing. But it’s okay, in fact it’s probably a good thing to admit that you’re afraid because once you do, you can work through it and get past it.