Context - Part 2, REAL goals
If you have a band, take each new song you learn and place it in your set to give it context. Not only does playing a new song with the band in an upcoming gig give you the impetus to practice hard, the great thing about having a band is that you have the opportunity to use your new and old material often... the licks, movement and technique stay active in your playing.
I don't gig often, so I when I get a high-profile gig, I use it as an opportunity to write something new.
Since most of you will not have a band, you can place that new song on the bandstand via a local jam session.
Even before the jam, tell your friends on "such and such" date you'll send them a recording of your new song (recording on your home computer with a jam track is just fine for this purpose). It's like a concert via email... you hype up that you're working on a new song and that you'll send it out on a very specific day. This helps to again put the carrot in front of you so that you work hard to finish the song in time.
It's nice to set goals, but if you put a date out there that "it HAS to be finished by"... a gig, recording date, jam session with friends (they'll keep you accountable to going) or a email "release" date... the desire to do a great job (and fear of public humiliation) is front of you!
Set a performance date right now for your new study song.