Just try to let it roll off your back. This will happen to you a lot at white belt. You end up going against other white belts who have wrestling, judo, or sambo backgrounds. Or sometimes you go against guys who are just naturally pretty good. Really strong guys, flexible guys, etc... You think you should be better than them but they beat you. Then at blue belt you will run into the sandbaggers who have been blue belts for like 5 years.

In BJJ there's a huge focus on how long you've been training and how it correlates to your skill level. The truth is, if you think like this you'll always be finding guys that you "should be better than" but aren't. Then you'll lose and try to find ways to rationalize it. Instead, just accept your fate. You're not a prodigy, there will always be guys like this, try to learn from the experience.

I had a guy who came into my gym with no grappling experience and basically tore up all the white belts, including me. He got his blue belt way before me, though I'd been training longer. But life made him give up BJJ for a year or two and when he came back I was on a totally different level. Just keep training, most of these guys who crush you "unfairly" at white belt will wash out (as most everyone does). If you stick with it, eventually you'll be a higher belt and probably be able to crush them at will. Hopefully by that point you realize it doesn't matter.

Last note, don't feel bad about having a bit of an ego tantrum. You can't just snap your fingers and change how you're feeling I'm a strong, aggressive guy in his 20's but I used to get so mad when I had a bad day that I would be on the verge of tears when I drove home from the gym. Now, if I get my shit handed to me I probably obsess about the rolls a little more then normal but I don't get upset, shit doesn't phase me.