If you want to look at your flight's recent performance to hopefully ease your mind, you can look it up on flightaware.com. I like to check our flights ahead of time, and at least once before (when JetBlue was allowing free changes), we switched from one set of JetBlue flights to another, with better on-time performance, when we realized the ones we'd initially chosen were routinely 2-4 hours late (due to the particular aircraft for that flight starting its day in an airport in the Caribbean that was itself plagued with delays). That's not the norm, though: usually our JetBlue flights have a pretty good record for on-time arrivals, even in the afternoon and evening.