Being motivated to study is probably one of the hardest things to do. After I took my GMAT the first time, I wasn't satisfied with my score and decided I would try to take it again. I gave myself a 2 week break but that slowly turned into a 3 month break. I've finally begun to study again. Basically my motivation now is knowing that my score just isn't good enough to get into the schools I want to go to. I've also taken away some of my distractions (xbox and tv) so I won't be tempted to break away from my studying. This is slowly working and I'm getting back into the flow of studying.
You really can't let your poor performance let you down. You have to remember to practice as much as you can because with enough practice you can reach your goal. For CR and RC, I used my wife's old LSATs. After doing the LSAT CR
& RC, I found the GMAT questions to be super easy. For SC I used the MGMAT book
but I didn't find that to help me out too much (just way too much information). I began just practicing as many SC questions as I could get my hands on, and I was finally able to recognize the traps in the questions.
Remember, just keep practicing, try to keep your anxiety down while going through tough questions and keep your distractions away.
Hope that helps out a bit.