When you invite trouble, it's usually quick to accept.

The line is a compact warning about self-sabotage and avoidable risk: if you behave recklessly, provoke conflict, or dwell in destructive habits, misfortune tends to arrive faster than you expect. Framed as an “invitation,” trouble is personified as something eager to respond—suggesting that negative outcomes are not random but often enabled by our choices. In a narrative context like P.S. I Love You, it can function as practical advice about grief, impulsive decisions, or emotional volatility: when someone is already vulnerable, courting drama or danger can quickly compound pain. The aphoristic tone makes it memorable and moralizing without being overtly preachy.