The winger penned terms to 2024 this week.
"I'm where I want to be and very happy with how everything has turned out," he said. "I arrived in pre-season with a lot of desire and enthusiasm to show my virtues to the new coach.
"There were a lot of players and I didn't know what would happen, but I think I've earned his trust.
"My dream is to be here, I know how difficult it is.
"As soon as the club saw that I could continue, I didn't have any objections.
"I'm going to try to prove on the pitch when I have minutes that I have the level and ability to be here."
Morcillo was on loan at Real Valladolid during the second half of last season and, despite not playing much there, he believes his loan spell was very positive.
"I'm a more mature player with more experience. I am aware of how difficult it is to be here. I knew what I had to give to stay."
Finally, the player from Amorebieta acknowledged that he feels very much loved by the fans.
"I think that we are public people who are exposed to all kinds of comments. People have the right to give their opinion and say what they think, but always with respect. I'm trying to do what I like the most, enjoy football, and I'm going to try to make people who doubt me look at me with different eyes.
"Athletic's fans are special, we like to feel their encouragement close to us, we need them and they are there at every ground we go to and they give us a lot.
"It's not all bad reviews, I also get a lot of praise and every time I go out onto the pitch I notice it a lot and, personally, I still get goosebumps."