Zones of Thought/Tear Jerker

When we finally find out just what made Pham Nuwen so bitter. Pham spends most of his life working to turn the Qeng Ho traders into a true interstellar civilisation, free from the usual cycle of collapse, working with his lover, the woman who first took him from his barbarous homeworld as a child. When he uses his centuries-in-the-making meet-up (note that faster-than-light travel is impossible in A Deepness in the Sky) of representatives of every Qeng Ho dynasty across human space to rescue the system from collapse, Pham pitches the idea to the families -- only to find that his lover has, behind his back, convinced them to vote against it. Because it would inevitably fail and destroy the Qeng Ho. Then she places him and his supporters on a fleet of ships programmed to spread out across the length of human space, to make sure he can never do it again.