A Bird in the Hand Is Worth Two in the Bush
Be content with what you have or you may lose everything.

What you have is more valuable than what you might get. In these case a hunter has already caught one bird. The hunter sees two more birds in the bush - two is better than one! In order to capture those birds, the hunter would have to drop the bird that is already caught. The hunter might not be able to catch them and will have nothing. The idiom can also be shortened to "a bird in the hand".

"Even though the money isn't very much, I should take the job because a bird in the hand is worth two in the bush."

"Should we accept their offer or go to court?"

"Let's take the bird in the hand."