Did you promise yourself you would consider it after getting a job or that you would buy it when you got a job? If the latter, I'm going to buck the trend and say follow through on your promises to yourself. If you don't believe you will come through, future attempts to motivate yourself are going to fall flat.
Realize, though, the reward is consuming nearly an hour and a half of your life just to make a cosmetic color change. If the reason you are even asking at this point is that the reward is no longer appealing, then do something else with your $15. Saving it would be best, but if that feels like a bait and switch, figure out what a fair trade for that quantity of your life looks like.
And in the future, consider how your commitments will affect you before you make them. Even if you just buy the watch, that's a pretty cheap price to learn this lesson.