Hitting a Plateau

Do you ever feel like you've hit a plateau?  Like you are just stagnating at a certain level?  Like no matter what you do you just can't seem to improve your weaknesses?

This is how I feel right now.  I know all the things I need to do but I just can't seem to make my game change.  I need to make my mind think quicker and retain more knowledge...but I can't figure out how to make it do this.  I learn things in class, drill them, and understand them, but as soon as the day is done I seem to forget how to execute them.  I spar and my coach yells for me to do things but by the time his voice processes through my head and I think of what he is saying the opportunity is gone.  I see openings but by the time my head processes what to do the openings are gone.

....I have my good collar grip, I'm breaking the posture, I'm going for the choke -- he postures waaay back -- ooh, I should hip bump sweep.....

Do I get it? NO.  By the time this thought gets to my brain the opportunity is gone. 

It's the same with transitions.  I know how to transition from one thing to the next....but when I spar my mind seems to forget.  I shoot a triangle, they posture.  I know I should switch off to an armlock or an omaplata but do I do it? Of course not.  The thought doesn't even seem to cross my mind.

WHY??? I don't understand this.  I have been doing jiu-jitsu for years, why am I having so much trouble all of sudden?  I need to be quicker and transition faster.  I know these things, but why can't I do them?

No matter how hard I try, it doesn't seem to be enough.  The harder I push myself the more I seem to shut down.  I go into class thinking about my weaknesses with the plan to conciously think about them and try to fix them.  I try, and try, and try, and the harder I try without results the more frustrated I get.  I push myself more, I tell myself to relax and not get upset, but I can't.  I go insane.

I feel lost...

I don't know what to do to take myself to the next level...

I need help...