What does Galatians 6:9 mean?

Doing good doesn't always seem to "work" in the short term. Especially doing good to your enemies, which Christians are called to do. It's an exhortation not to give up on what's right simply because there's no immediate temporal payoff. Ultimately the command is not about getting people to like us or respond to us nicely, but about showing the love of Christ and developing a spirit of service and humility. That's at least one harvest reaped by persevering in kindness.