The student tries, exaggerating the problem to show how difficult it is. The instructor suggests another solution. The student wants the perfect technique to magically appear, without effort. Uke weakens the attack to give tori a better chance. Tori is more able now, and succeeds against a less effective attack.
Tori feels better while the technique suffers.
Tori and Uke switch roles. The former tori attacks with a blast so the resulting technique requires a rugged fall. When the student complains to too much force, tori reduces the focus of the attack to spare Uke. Uke fakes the fall. The technique suffers, the risk is removed, and the reality is gone.