Be aggressive about standards and patient with learning.

Two settings are needed and they are easy to mix up. What you accept in finished work can be very demanding without doing harm. What you accept in the process of becoming able to do that work has to be forgiving, because learning involves being bad at something for a while. Applying the demanding setting to the learning stage stops people before they start.

Separate the two out loud when you are teaching yourself something. Hold the standard for what counts as good and drop it entirely for what counts as an acceptable attempt today. The standard is what you are aiming at, not what you should already be hitting.