I’d suggest you pick one of your bread and butter workouts. For me this would be 30/30s or something with race start intervals. These typically feel like workouts that are hard, but I’m pretty good at doing.
This could be totally different for you, but pick something you have confidence in doing and stay in your lane. Maybe grab an easy endurance one if you want, but if you’re looking to dive in then pick something hard that plays to your strengths