Capacity to Be Critical--

This is really a hard skill.  I think mostly we fall into two diametrically opposed categories: either we find ourselves flawless and we defend our work to the death (even when our effort is small compared to our relative capacity), or we tell ourselves that we're horrible and use our horribleness as an excuse not to try too much.

The hard skill is of self-criticism, such that you (or I) can improve, even when our ego is bruised.  Such that we can look at our own work and say, even when we want otherwise, that it needs work.

It is the capacity to do work and continue to do work instead of complaining, flagellating, or making everyone else the enemy.