Not a first solo ,but something that instantly helped the penny drop to get me off solo.
I already had some prop and jet solo time when I decided to go on an RAFGSA gliding course in 1974 .
I was making a right pigs of air brake control on finals in a K 13, porpoising merrily down to Terra firma, sometimes yards away from the proper touchdown point. My instructor was Rick Heselwood ,a well known personality. "FFS Haraka!" he said, after the third switchback ride: "Look!" ( cranks airbrakes in and out) "treat it like an effing THROTTLE!!" Problem solved: two launches later, "Off you go".
Thanks Rick (RIP)