At last, you've earned your brown belt.
For one thing, you're not the "new guy" anymore! You know how to fall pretty well by now, so you don't look to awkward out there. You know some names, your appearance in class has become almost expected, you know a few inside jokes. You're one of the gang! Heck, you even get to be the "senior" partner sometimes! Life is good.
Then you notice something. Every time the black belt leading the class needs to demonstrate something, he picks... you. You notice that this means you fall down—a lot. In judo, you get thrown down, a lot. You get arm barred and choked and pinned. A lot.
What's going on here? Why are they always picking on you, for crying out loud?
Well, here's the funny thing: you're actually lucky. For starters, you are more than likely singled out because you make a good uke, which means, you have good ukemi and a good working knowledge of the material. Take it as a compliment!
It's also a time to relish, because you're getting to feel first-hand what a technique should feel like from some very experienced teachers. Seeing a sensei perform a technique is one thing, feeling is quite another. Take this blog post for example, where a student talks about the difference it made when she experienced the technique first hand.
You might think of it this way: Lowry Sensei always talked about the process of learning from the part of uke as being like a film negative. Expose that blank negative to light, and once that negative is properly developed, you can produce an endless number of “positives” or prints.
Even now, I'll jump at the chance to uke for those who are my senior whenever I get to be around them. So enjoy being the "punching bag" while it lasts. Believe it or not, your budo will grow by leaps and bounds when all is said and done.