Guiu began the season on-loan with Sunderland before being recalled by Chelsea on deadline day.
"We initially decided to go to Sunderland with great enthusiasm and excitement to get some top-flight minutes and gain some experience," he told RTVE.
"In the end, Delap got injured and I had to return to Chelsea, now with great enthusiasm and training hard every day.
“When (Nicolas) Jackson said no to returning from Bayern, they called me, we talked about it, and it was quick. Ultimately, I want to be successful at Chelsea. And that's how it was.
"It was all a bit chaotic, but ultimately, I'm a person who approaches everything with the utmost positivity, and that's how I approached it, enjoying every moment, because a footballer's career is short.”
On Sunderland, Guiu added: There has never been any disappointment. I believe that every action I take in my career is because I want it. Now I fight every minute, in training and in matches, to play as much as possible. Now I fight every minute, in training and in matches, to play as much as possible. Now I am at the best club in the world.”