Steering a cruiser close-hauled in darkness is largely a matter of feel. As the boat runs off the wind, heel angle may increase, and the boat will slow down when she comes fifteen degrees or more below her best course. As she luffs above the optimum, she will come upright and lose way before the sails begin to complain. The first two become noticeable as soon as a yacht is more than five degrees high, so this state is easier to spot than being below the course.
True expertise comes with time, but if you are still waiting for it, creep slowly up to windward every few minutes, wait for the symptoms, then bear away just enough to get her going again. Note the compass heading and stick with it for a short while. Then repeat the experiment. You won’t go far wrong.