Rain is one of the rows on the record because it changes almost everything a little.
Leave at least twice the gap to the car in front: stopping distances can double on a wet road. Use the brake and the accelerator gently, and steer smoothly, so the tires keep their grip.
Put your dipped headlights on so others see you, and keep the windscreen clear with the wipers and the blower. If spray from a truck blinds you for a moment, ease off and hold your line; it passes.
We book at least one lesson in the rain for every learner before the test (sample). It is calmer than people expect.