“Sometimes, when you want to repair something, it almost falls apart, and sometimes it is impossible to open it without destroying it. … And once you have it all apart, it can be quite tricky to reassemble everything because you forgot how everything fits together.” This short article by Stefan in Medium explains How to take things apart without breaking it too much. There are some useful tips in this article.
Understanding how to get into your device is often the first step to repair. You might simply need to clean it or or change the battery or replace a component.
If you are interested in repair, a useful way to learn (without destroying your precious devices) is to practice on old devices that are deemed beyond economic repair. Most repair technicians and students learn this way. Taking things apart and then (trying) to put them back together. Those skills once learned are with you forever, so do not look upon it as wasted time.
For more information and help about repair, check out the Resources page, with links to self-repair, community repair and more.