Join an existing team or form your own. It really helps you. For me, I know that I can turn to my team for support - and also that they are counting on me too. I feel accountable not only to myself, but to my team. All of this helps me to stay on track.
Bonus - if you recruit more members to your team and get people to sign up for Sparkpeople, you get 10 Sparkpoints for each person who joins!