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
Some to the forest, some for firewood.
Your own shirt is closer to your body.
The quieter you go, the further you'll get.
You can't help grief with tears.
Each sandpiper praises its swamp.
Start taking care of the dress while it's new, and of your honor while you are young.
A bad example is contagious.
If you like sledding, you should like to carry the sled.