grass is always greener (on the other side of the fence), the

the grass is always greener

or

the grass is always greener on the other side of the fence

If you say the grass is always greener or the grass is always greener on the other side of the fence, you mean that other people often seem to be in a better situation than you, but in reality their situation may not be as good as it seems. You know what it's like — the grass is always greener on the other side of the fence. I'm always looking at jobs advertised online and thinking I'd be better off somewhere else. Note: Grass and greener are often used in other expressions with a similar meaning. A lot of players who have left in the past have found that the grass isn't always greener elsewhere. I cannot have my staff believing that the grass is always greener in another company.
See also: always, grass, greener
Collins COBUILD Idioms Dictionary, 3rd ed.

the grass is always greener

other people's lives or situations always seem better than your own.
This is a shortened form of the proverb ‘the grass is always greener on the other side of the fence’, usually used as a caution against dissatisfaction with your own lot in life. There are a number of sayings about the attractions of something distant or inaccessible, for example blue are the faraway hills .
See also: always, grass, greener
Farlex Partner Idioms Dictionary

grass is always greener (on the other side of the fence), the

What one doesn’t have always looks more appealing than what one has. A proverb first cited in Erasmus’s Adagia (1545), this maxim remains true and the phrase remains current.
See also: always, grass, greener, of, other, side
The Dictionary of Clichés by Christine Ammer
See also:
  • as always
  • it was ever so
  • twa
  • it was ever thus
  • thus
  • you can't always get what you want
  • never fails
  • always be on (one's) guard
  • first step is always the hardest
  • the first step is always the hardest