Лучшее – враг хорошего

With accent marks:

Translation:

The best is the enemy of the good.

Meaning:

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.