Congratulations on aging. It must've been seriously difficult for you.

The difference between someone making you a birthday topic and you making your own birthday topic is all about topics. When someone makes it for you, the topic is right there: "It's ____ Birthday!" When you make the topic is, like, "Hey, it's my birthday yeah." The first one is an example of a good topic, whereas the latter is a fairly weak non-topical topic. Congratulations on that, too.

My 21st birthday was pretty uneventful. I had already legally gambled before I turned 21 and I had already consumed alcohol illegally. What else is there to do?