Having someone to work with, give you ideas, goad you on, share your misery and read your responses to RFPs helps a lot. Good business development requires a certain amount of self-perspective. It can get pretty dark and lonely if there's no one to talk to about victories and defeats. For some, the listener is a partner. Others team with a secretary, work with a core group of lawyers or involve themselves in myriad other arrangements designed to scare away the lonelies, inspire creativity and expand reach.
Success breeds more success.
When you're doing well, you look the part. Confidence goes up, risk taking goes up. The better you feel about yourself, the more likely you are to be able to focus on what's right for the client instead of what you need. The best opportunities come along when you're eyeball deep in a big case. It's one of life's little paradoxes.