A great UI designer once recommended redrawing a well-designed app, to understand proportions, and understand balance, flow, etc. This may come across as very puzzling to many of you, but I actually learned alot from this exercise.
First, it made my 2-3x better at using Sketch, and raised my confidence in quick and dirty icon design/production. It also surprised me just how much space there is. You seemingly can't have enough space between elements, items, etc.
Fun exercise, it took me quite a while, but it was kinda fun. I'll probably do a few more apps on here, in addition to my own production work :)