With accent marks:
Лу́чшее – враг хоро́шего.
The best is the enemy of the good.
The author of the phrase “the best is the enemy of the good” is considered to be the French philosopher and writer of the 18th century Voltaire. He wrote it in his “Philosophical Dictionary” and the novel “Impatient” ("le mieux est I'ennemi du bien"), although such thoughts were expressed by many others including Shakespeare, J. Bruno, and so on.
The interpretation of this phrase varies, but in Russia it is often understood in the sense that in striving for the best, people often spoil the good.
Other Russian proverbs
You can't spoil the porridge with butter.
Start taking care of the dress while it's new, and of your honor while you are young.
Poor people are inventive.
If you like sledding, you should like to carry the sled.
Put your trust in God, but don't make mistakes yourself
Measure seven times, cut one.
Оne sees the mote in another's eye and ignores the log in his own.
Some to the forest, some for firewood.