De Gea joined United in a £18million deal from Atletico Madrid last summer. The goalkeeper was axed in January following a string of blunders.
But an injury to Danish keeper Anders Lindegaard saw De Gea get recalled by Ferguson.
De Gea said: “No-one likes to go to the bench, but perhaps it helped me reconsider and realise that I had to keep fighting.
“That has helped me become much stronger and confident. I’m getting to my best level now.
“Any player should learn from his mistakes to improve every day and know his weaknesses.
“I’ve done things pretty good, I’m happy with my performance so far and I’m sure I’ll go further.
“I’m young and I have only just come to a league and a country that is different from mine, so I shouldn’t worry.
“Sir Alex just told me to adapt and continue as I am and the results will come.”
