the spirit is willing but the flesh is weak
the spirit is willing, but the/(one's) flesh 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 flesh 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 flesh is weak.
the ˌspirit is ˈwilling but the ˌflesh (it) is ˈweak(saying, humorous) you intend to do good things but are too tired, lazy, etc. to actually do them
spirit is willing but the flesh is weak, the
I would like to do this but I don’t have the willpower or strength. This term comes from the Bible. Jesus, counseling his disciples at the Last Supper, said, “Watch and pray, that ye enter not into temptation: the spirit indeed is willing, but the flesh is weak” (Matthew 26:41). John Lyly was more specific (Euphues, 1579): “The delights of ye flesh are preferred before the holynesse of the spirite.” Today the term often is a rueful admission of physical weakness, much like I would if I could but I can’t (also based on ancient proverbs).