There are plenty more fish in the sea.
There, but for the grace of God, go I.
There is no place like home.
There is no royal road to learning.
There is nothing new under the sun.
There's safety in numbers.
Those who live in glass houses should not throw stones.
Time heals all wounds.
To err is human(, to forgive divine).
Two's company, but three's a crowd.
Two of a trade never [seldom] agree.
Two wrongs don't make a right.