This life doesn't come with a manual book. Often times, you have to learn everything autodidactically. Sometimes you choose not to learn but win your ego. The one which helps you survive. However, retrospectively you can set aside that thing to reflect. But somehow retrospective learning is slow and late.
Simple lesson you get from experience can help you navigate better. Some people don't like it when you fold the corner of a book. They hate it to the point they will cut off the friendship. The lesson; be careful next time you borrow your friend's book. Don't forget to apologize after making that mistake, so no social bond must be sacrificed. Even though an apology doesn't guarantee that. At least, it will reduce the risk. So, nothing to lose. Lower your damn ego a bit, probably.
I thought folding book's paper wasn't a big deal. While I was staring at his annoyed face, I wondered, what was really wrong? Why it made him angry. I didn't get it. I remember I didn't apologize since I didn't get it. Then, years after. When I reflected on that, I know how annoying I was. We don't know how someone treasure something carefully. Of course, they will get angry when you come in and ruin everything. Humans' values are varied, so don't overlook them.
I don't know where this life will lead me, but surely, I still have a lot to learn. Maybe I must make a certain mistake first, to learn next. But somehow, it's fine. I suppose, my current self can regulate emotion better. So next time I encounter with difficulty, I can persuade myself, that it's temporary.