The people I train with are faster, stronger, more athletic,and pick up the moves more quickly than I do. I also have less time to put into it.
Would I like to advance in rank some day? Of course, but how I'm measuring my progress is that I'm still showing up. Every time I step on the mat is a small victory for me.
There are people who haven't even started, quit and come back who will pass me up with regards to rank, but if I can do still be doing this when I'm 60, maybe I can still do it when I'm 65, and so on. The rank will resolve itself.
Below is an excerpt from White Belt Jiu Jitsu, written by a five year white belt. There is a lot of good advice here, that I'd recommend to anyone training in any martial art, at any level. The full post may be read here. Enjoy.