As an experienced instructor I have frequently been brought in to help students struggling in the circuit. Every single time the problem was the fact that the foundation flying skills were not there, usually because the instructor had rushed through critical ex 5 to 9 manoeuvres and then progressed to the circuit too quickly.
To fly a proper circuit you have to be able to fly a balanced climb at a constant and correct airspeed, make a balanced climbing turn, level out and set the cruise attitude and trim and then manage a level turn a descending turn and a final approach with the aircraft pitch attitude set and held to maintain the target speed and with aircraft in balance and trimmed. If you are still struggling with this then you should not, IMO, be in the circuit
Before going to the circuit I always start by having the student fly some practice circuits in the practice area. The airport is set at 2000 ft AGL and circuit height is 3000 ft. The students starts at 2000 ft establishes a climb, turns 90 deg at 2500 ft turns again at 3000 for the "downwind" sets cruise power does the checks etc then turns on to a base leg starts the descent, turns to final and at 2200 performs a go around. He/she doesn't have to worry about finding the runway following traffic etc, they do concentrate on aircraft control.
The OP might suggest this to his instructor