what i did... was start writing down what i can play (a scale or arppegio ect.) and at what speed on my metro. then i had concreete evidence/proof of what i could do and what was lacking. then i worked on getting everything up to the same level. Then when i had a bad day playing i could look at my chart and see that i was indeed having a bad day becasue i have played (what ever it was, a song, lick, solo) that fast before so it made me feel better and try to strive to get back up there.
knowing your achievements helps you to build off of them to achieve more!
give it a shot... might just work
P.S. Dont just learn all the time take time to write. it takes time just like everything else to become a good song writer. so practice that just as much as you practice everything else. youll get better just stay focused and postive
good luck