Antonio Banderas has described how he had to “kill” his former self to play the role of an ageing film director modelled on Pedro Almodóvar for the director’s new film, which has premiered at Cannes.

The Spanish actor, 58, said that, following heart problems, making Pain and Glory had helped him reassess his acting and his personal life.

“To create this character I had to kill Antonio Banderas. There was something in me that I could definitely not use for this role,” he said on Saturday.

However, Banderas said, the experience of making the film had been the happiest in his career. “This is something that no one can take away from me. Pedro wanted me to show something new in the character. Maybe become a new Antonio Banderas.”

Pain and Glory recounts a version, part fictionalised, part fact-based, of Almodóvar’s troubled private life, and details a reunion with a lost love after several decades. One of the film’s most powerful scenes culminates in a kiss between Banderas’s character and his former boyfriend, played by Leonardo Sbaraglia.

It was, Almodóvar told journalists, a rare thing to see on screen. “I have never dared to kiss anyone in such an intimate way,” he said. “Two 50-year-old men kissing with so much passion and excitement on screen is not often seen.”

He said the plot line drew on a true personal story.

“I did experience a love that was aborted, that was broken. When you have to separate from someone you still love you have to set yourself free as if you were cutting off your arm. I have not had the reconciliation you see in the film.”

The work, which is in competition for the Palme d’Or and received a standing ovation on La Croisette, also looks at the subject of addiction, both to illegal and prescription drugs, and at artistic creation.

Penélope Cruz, whose role in the film is inspired by Almodóvar’s mother, said although she was familiar with working on his films, she was fearful of asking him questions because he had “given his guts, his story” to the script.

Late in the film, when she is frailer, the mother tells her director son she does not like how he makes films about his life using the genre term “autofiction”.

Almodóvar said this scene gave voice to his wariness about telling a story too close to his own life.

“When you talk about yourself you necessarily talk about other people’s lives as well, so you have to be very careful when you do it,” the director said. “My life is reflected in the film but it mustn’t be taken literally. All these things represent me, my way of feeling. I can’t give the percentage of what is real. There is a mix.”

Almodóvar said the film was not his last will and testament and that his own addiction was to making cinema. He was already writing two new projects.

An emotional Banderas, who was married to the US actor Melanie Griffith until 2015, said he believed the film was about more than addiction; it dealt with “the circles in our life that have been left open with family and lovers”.

“I couldn’t believe when I read this script that he [Almodóvar] was calling me to act his character. I told him I was at his service to find the truth and start from scratch.”

He compared the director’s artistry to that of other Spanish creative geniuses of the past, Federico García Lorca and Salvador Dali. “People need to see the reality of what Spain has been through in the last four decades and so people need to see Almodóvar’s films.”