Hmmm...maybe a nice long trailride/picnic would help you out. Just a very relaxed day to go and bond with your horse and not have to worry about lessons. Take a lunch with you maybe so you can find somewhere and just tie your horse and just eat, relax, (bring some yummies maybe for the horse) and just vent with your horse but make it positive. I know it sounds silly but sometimes when I get bored of doing something and just feel blah, I just take a nice long trailride, it seems to ease my mind and it helps me concentrate on the next day with my horse.
Sorry you feel blah, and hopefully you perk back up. I have been through it before so you are not the only one.