HinKhoj Dictionary

always chasing rainbows - Constantly pursuing something more appealing than what one currently has—no matter how unrealistic it is.
at the end of the rainbow - Said of something that is appealing but seemingly illusive or very hard to obtain.
chase a rainbow - To pursue some goal or accomplishment that is utterly unrealistic or unlikely to happen.
life isn't all rainbows and unicorns - Real life does not just consist of innocent, carefree happiness; there is more hardship or suffering in reality than one realizes.
no rain, no rainbow - Positive things usually happen after or alongside bad things.