A psychology teacher explained muscle memory like a path through the woods. The more you take the path, the less debris is going to be in the way and it will feel easy. When you get injured or take long breaks from skating, it gives the woods time to grow back over the path = you feeling rusty. Sometimes it’s easy to develop a bad habit in a single session which is why it’s important to not obsess over a single trick you can’t do one day. I liken this to a huge tree falling over on to the path. Developing these bad habits can happen for a number of reasons. Fatigue, new shoes, a chipped board/ waterlogged board, a new board, new terrain, wind, etc. can lead to developing a bad habit within 10 tries unfortunately. When I’m struggling with something I think it’s important to focus on the base physics of how a trick works, rather than all the little details. Because at the end of the day, it’s the physics that make a trick work, and the details that give you style. The details can always be figured out later and come natural after lots of practice.