What helps you actually stick to the Pomodoro technique?

I’ve been working on NAT.POMODORO, a simple productivity app built around the Pomodoro technique.

While building it, I wanted to keep the experience focused and practical rather than overload it with unnecessary complexity.

I’m curious how other people use Pomodoro in practice: what helps you stay consistent with it, and what usually makes you stop using a Pomodoro app after a while?

I’d especially like to hear which features you consider essential in a Pomodoro timer.