As I'm just starting out fitbitting (placed an order for a tracker but it will take a little time to arrive) I've been thinking about this myself.
One of the things I do doesn't cost me anything; there are some reward programs available that you can sign up for, depending on your location. I believe there are even some health insurance companies that also support such reward programs which can save you a lot of money, or help you get discounts or free stuff.
I'm also considering setting aside a set (small) amount for every goal I reach. One of my hobbies is the guitar, I'm still in the process of learning to play, but maintenance etc does cost a little money. So if I set aside money for every goal reached, I can use that to buy new strings or eventually to save up for a new guitar. Maybe you have a hobby or ambition apart from the health/fitness side that you could partially or fully fund through a similar personal reward system?
If you care about beauty, relaxation and wellness you could look into giving yourself a treat in that department. Go to a beauty salon, get a massage, a mani/pedi.
My point is; think about what makes you happy. Be that saving up for something you want, indulging in something you don't get to do often, or experiencing something you've always wanted to, but never did. It doesn't all have to be expensive or big. If you want some relaxation you could just get yourself some products and plan a night in the bathroom with a glass of wine, a hot bath and a bunch of beauty products. If you like gardening you could just allow yourself to buy that one plant. Reading, get that book you've been eyeing for weeks. I'm sure you get what I'm saying 🙂
