I think that the reason why we can have a hard time maintaining progress is because we don't take the time to appreciate how far we've come.

Looking at where you are now in terms of how far you've come instead of how far you have yet to go not only promotes a healthier mindset, it promotes more consistent progress. 

A lack of gratitude feeds the danger of self-sabotage - the "stop, go, stop" dilemna.  It makes you undervalue what is working and going good in your life and focus on what you think is going wrong.  The result of that is you stop doing what's working and you never feel satisfied. 

Developing an attitude of gratitude is hard, intentional work.  But it's the key that unlocks the fullness of life no matter how far you think you have yet to go.