Converse Umeshism: "If you never miss an opportunity to get something by asking, you're asking too much."

Possible more colorful version: "If you've never missed out on something you needed because you didn't ask, people find you too greedy."

Overlapping Umeshisms: If you don't ask for enough, people will still think you're greedy. If you ask for too much, you'll still neglect to ask for things you could've gotten.