Motivation comes and goes! You won't always be motivated so you can't rely on it to take action.

Relying too much on external goals and rewards can actually have a negative impact on your motivation, as once you achieve that reward or goal you'll probably have a drop in motivation.

It's fine to have drops in motivation from time to time, everyone will experience that.

But the people who stay in shape all year round don't rely on externally motivated, they're internally motivated and still stay consistent even when their motivation is low.