How do you keep from losing an SD card?

This is not an important question, more like a curiosity google can't answer(yeah I know...or maybe I suck at googling). I got an mp3 player for christmas and I was learning to use it(not really that hard...it's my first mp3 player, and when I first saw it I was like wtf how can this thing work it is like 2 square inches small!! I actually wonder how I will not lose the mp3 player itself). Then I got into learning ABOUT it. Mainly, before I had it I did not understand or comprehend what 4 gigabytes is(I can't even remember how megabytes and gigabytes and bytes differ by heart). It's like 50-100 CDs! I was also surprised that it can play radio and record, and it can record voice or radio, very cool. Um anyway, I read that if I wanted more storage capacity(compared to the mp3 player my computer has a ridiculously huge music collection...) I can extend it with an SD card. I also read that people have them for different activities or genre playlists to separate their playlists. I then found out you need an sd reader to use it. I mean I don't plan to need the extender or reader...but let's say in the future I do. I could end up with a collection of little sd cards!! How would I not lose it? Is there an sd card "album" like a cd album so you don't lose them? How can I avoid losing such small things?