Sometimes you are not afraid of failure; you are afraid success would remove the excuse for never becoming more.

As long as you have not really tried, the question of what you could do stays open, and the potential remains intact. Succeeding closes that: you find out your actual size, and the comforting explanation that you simply never applied yourself is gone. What looks like fear of failure is often fear of a verdict, and the verdict requires a genuine attempt to arrive.

If something keeps getting postponed, ask what you would lose by finding out how good you actually are. Then make one real attempt at a modest scale. Almost everyone discovers they are neither as capable nor as limited as the untested version suggested.