Challenging experiences are the most educational and so, ultimately, beneficial.

One cannot change one's nature, no matter how much time passes.

Do not seek advice from a biased party.

Alternative form of never meet your heroes

One must take risks in order to achieve a goal; success requires enterprise.

There will always be problems in a romantic relationship.

(obsolete, dialect) The houseleek.

People tend to take things for granted while they are available.

(informal) Once a person of another race has a sexual relationship with a black person, they will not return to having sexual relationships with members of the former race.

Alternative form of you never miss the water till the well runs dry