To keep myself motivated I got involved with other musicians, got together and jam regularly. We have so much fun making music, and it makes it easier to keep at it because you actually start looking forward to playing with them.
I also make sure my guitar is in reach, so I can grab it when I want to. Worst thing you can do is keep your guitar packed. Make it as easy as possible and as much fun as you can.
If you're a busy person, try to schedule time for yourself when you can play and have fun with your guitar.