Coffee can improve memory but it's only a short-term boost. It's similar to when you toss something oily onto a lit BBQ, the flames will shoot up high but only a brief moment. I can relate to feeling sleepy because I'm a night-owl, even right now it's almost 5 am and I'm posting!

What I've always found is when you're trying to work on something but you cant focus no matter what, then stop trying, it'll only aggravate you. Myself, I cook because for whatever reason, when I cook, I can relax and I just get a flow of ideas for the stuff I was working on, then I finish cooking, eat and pour out all the ideas.

I'm a naturally very relaxed person because I just rationalize that no matter what happens, the impact is going to be minimal. Even if Murphy's Law is true and a few days become an unstoppable train wreck, I just keep telling myself, "OK, it sucks that happened but it could have been so much worse" and that reduces my anxiety quite a lot. If you cant concentrate much because of the anxiety, try telling yourself the impact is not severe, it's very minor. You don't need to do the entire project all at once, do it in bits and set a schedule where you'll do fragments of it. Make the fragments small and feasible, so once you've completed it, you can look at your list, check it off and tell yourself you're one step closer to finishing it. That one tick-mark can bring quite a lot of motivation and reduce the anxiety because you've shoveled a pile of stuff off your plate.