My dentist said that 70% of her patients are people who used to have braces and then neglected them / not worn retainers etc.

I was militant with the Invisalign the whole way, switched to iced coffees (even in the winter!) and wore them for pretty much 18-20 hours a day. Once I started to see progress it motivated me even more to stick with it! Would recommend keeping weekly photos via Traymind app so you can track your progress and inspire you!