Getting tapped by lower belts is only a big deal if the submissions come from making "lower belt" mistakes: one arm in-one arm out, double leg into guillotine, crossing your ankles in back control, isolating and extending your arms under mount/side control, etc.
If you get consistently passed, smashed and destroyed, while making no technical mistakes in accordance to your belt rank, well, too bad, the other guy is better at winning. You need to fix some variables to offset that.
It's also interesting that there's people who are percieved as the "gym sharks", that are AWESOME during training and will tap you and everyone else consistently, but when they compete, they, well, suck, OR, the kind that are mat wizards, but if they stub their toe, they stop training for 2 weeks.
And then there's those guys who kind of suck during training, but they're gritty as hell when it comes to competition, go into beast mode, and smash people left and right.