We should never measure ourselves according to our "possibilities" because all such estimations of self are always based in secretly embraced evaluations of our own past; rather we ought to give ourselves over to what seems impossible to us because we are only truly fulfilled in this life to the extent that we are able to transcend who we have been!
The answer as to what is the best use of one's life is found in being present enough to oneself to detect and reject all of those useless thoughts and feelings that undermine our higher possibilities. Only then do we realize that letting go of these limitations is the same as serving our own highest interests, for our greatest potential is to be free!
Never believe in any negative thought or feeling that would have you believe, "There's no way!" Always remember instead that real life is a secret and vital flux of possibilities rising up from the ground of what seems improbable, much as a spring flower manages to bloom in a once frozen field.
Only those who never give up, who persist with their wish to find and fulfill the promise of themselves, make this truly self-liberating discovery: places once seen as being impassible barriers to happiness become as bridges to the same, but only if they are welcomed as a part of the journey.