the grass is always greener on the other side (the others' circumstances seem more desirable)

all's well that ends well

Alternative form of tutto è bene quel che finisce bene

all that glitters is not gold

well begun is half done / a good start is half the battle

to see the writing on the wall

good things come to those who wait

to give credit where credit's due

all's fair in love and war (unpleasant conduct is acceptable during love and conflict)

revenge is a dish best served cold