Why do I keep losing my embouchure?
Embouchure overuse syndrome
As the name suggests, embouchure collapse may be caused by "overuse"—or in simple terms, playing "too much." ... When a player is forced to continue playing despite this, the resulting stress can cause a chain of injuries that lead to embouchure collapse.
What happens to the lips when the correct embouchure is used?
Whether the player uses one general pivot direction or the other, and the degree to which the motion is performed, depends on the performer's anatomical features and stage of development. The placement of the mouthpiece upon the lips doesn't change, but rather the relationship of the rim and lips to the teeth.