Lightning Mcqueen goes through depression when he is getting mentored. He doesn't think that he can get back into racing and that he should just retire.
The Road Back
When Cruz wants to take Lightning Mcqueen to a small race he freaks out and doesn't believe he can do it.
Lightning Mcqueen goes in a racing tournament against Jackson Storm. In the middle of his racing he takes a pit stop and Cruz (his mentor) takes his place. Cruz wins the tournament and beats Jackson Storm. Since Lightning started he takes half of the credit and doesn't need to retire.
Cruz becomes a professional racer and races along side Lightning Mcqueen.