we cannot make the best of what we are if our hearts are always divided

I don't know how this works.

"One who is content in what he has, and who accepts the fact that he inevitably misses very much in life, is far better off than one who has much more but who worries about all he may be missing. For we cannot make the best of what we are if our hearts are always divided between what we are and what we are not." --Thomas Merton

My heart is always thus divided. But it is precisely the struggle to make the best of what I am and what I can be that divides it, that discontent that makes me struggle. So... what do you do then?