Hello dear friend!
I think I would agree with you mother. Spending your days without any activity is boring. Collecting stamps and coins is tottaly for kids. You should find a more interesting and not simple hobby.
For example, I have a hobby to take photos of people who I even don't know. This is very ambitious. I usually catch them sitting in the bus, eating, writing. I like it how they are not prepared and do not expect their actions to be captioned. For this kind of hobby I dont really need to be active as there are people all around me. Eventually, when I mix up all the photos together, I could even make a film. Without any talking, just some special effects.
I know a very interesting activity which I would like to try as a hobby. It is drawing on water with paint. Although I don't know much about it yet, I am looking forward to make a start.
Hope I encouraged you to do interesting things,