Great point from our pal javier.
Tennis can demand that you be a little selfish and play according to your own needs to realize your potential. If you feel like you're going through the motions too much, then something's probably bugging your or creating a distraction that's holding you back. That's something that you want to get sorted out if you plan to dedicate your time and effort toward your sport.
Trust me, you're at the point right now where good psychology will pay some of the biggest dividends you'll ever see. Your own expectations need to be grounded in reality or you'll be constantly disappointed with yourself and eventually want to bail on the whole scene. I've seen a few sluggers your age who were carrying too much weight around in their heads and it eventually wore them out. Sometimes parents might be too overbearing, or these developing players may just put too much pressure on themselves and find it impossible to measure up. That just spells gloom and doom, right?
If you love the game and honestly want to pursue some higher development - for yourself, not anyone else - then you'll make the decision to get going and you won't need anyone to motivate you. Okay, except maybe on those occasional days where you want to stay in bed instead of hitting it at 6 a.m. I've tried a few early morning outings myself lately... let's just say I really love good coffee! It may take a couple of weeks for you to really chew things over so you can make a decision, but if you recognize that deep inside you honestly want (or even need) to get better, that resolution will probably be your motivator.