We know what to do. Why don't we do it?
You're overlooking the nitty gritty
Imagining how good you'll feel when you've reached a goal is great. It's the part where you get excited and motivated. But dreaming about the future can mean you're not getting realistic about the obstacles.
There's a difference between imagining yourself stronger from a gym routine and imagining yourself getting out the door earlier in the morning for a workout. To get to the reward, you have to be mentally ready for the things in your way.
Try this: Program your brain with "if-then" thinking. If you miss a morning workout, you'll take an after-dinner walk. If you keep skipping your daily exercise, you'll make plans with a friend to do it together.
That way, you'll have solutions at the ready when you hit setbacks. And your bad days won't knock you off course.