First of all, it is very difficult to perfectly cover up your art by painting over it. More often than not, this change is slightly noticeable. These subtle changes provide richness and contribute to the final art.

Secondly,  each time we make a pass, we have the opportunity to revisit the principles we are learning about differences, composition, value, color, etc. LIke everything in life, the second or third time we try something we usually improve. It is the same with art. Trust that by letting go of something that is not particularly engaging, you will find something better on the next try.

Try to enjoy this process. This is what it looks like to learn. Treat it more like a game. In time, your ability to discern and create more sensitively will increase. The key to this improvement is the willingness to let go of something undeveloped in order to discover something that is more exciting and engaging.