I recommend (and already mentioned) journaling. In the journal, I visualize attaining the goal or write about ways to keep going.

Watch, listen or read stuff that motivates and uplifts you. And keep on doing it every day.

Try to motivate yourself every day and find what works. This quote sums up what motivation is, it is not something that is only done once:

"People often say that motivation doesn't last. Well, neither does bathing - that's why we recommend it daily." - Zig Ziglar