Re: Hi guys! Beginner here :)
Welcome! You don't need a lot of reasons to start. Just walk in the door. You'll find reasons to stay, or you won't, and you'll leave. No shame there.
A couple suggestions:
1. Consider not talking too much to your friends about your training. Clearly they've got opinions that aren't going to be changed by facts or by your actual experiences, and if you talk about them, they won't get it. If you don't want to become known as "Darwin who's all funny in the head about that aikido stuff", don't bring the subject up yourself, and if someone asks, just say, "It's going fine, I enjoy it" and leave it at that.
2. Keep your expectations to a minimum. Try not to formulate opinions about what your training is going to be like (or should be like), or how fast you should progress. The reality will always be different, in big ways and small ways, and the more you develop your expectations, the more likely you are to be disappointed in the reality and give up.