the spirit is willing, but the/(one's) body is weak

the spirit is willing, but the/(one's) body is weak

One has the desire or intention to change do something beneficial, but one lacks the resolve or motivation to do it. Every year I resolve to eat better and do more exercise; and every year, inevitably, the spirit is willing, but the body is weak. We all know someone who has the best intentions in the world to get their lives on the right track, whose spirit is willing, but their body is weak.
See also: body, but, spirit, weak
Farlex Dictionary of Idioms.

the spirit is willing (but the flesh is weak)

someone has good intentions (but yields to temptation and fails to live up to them).
This expression quotes Jesus's words in Matthew 26:41, on finding his disciples asleep in the Garden of Gethsemane despite his instructions that they should stay awake.
See also: spirit, willing
Farlex Partner Idioms Dictionary
See also:
  • spirit is willing but the flesh is weak, the
  • the spirit is willing
  • the spirit is willing but the flesh is weak
  • The spirit is willing, but the flesh is weak
  • the spirit is willing, but the/(one's) flesh is weak
  • back (one or oneself) into a corner
  • back oneself into a corner
  • backed
  • backing
  • get (one's) (own) house in order