Jason Segel admits he was 'really unhappy' at the time he was filming How I Met Your Mother

Jason Segel has opened up about needing a 'f*** it' attitude after being 'really unhappy' during the later seasons of How I Met Your Mother.

The actor starred as Marshall Eriksen on the long-running CBS comedy, but admitted to struggling in the later seasons of the hit show.

He said: "There was a period in my life and career around the last couple of years of How I Met Your Mother where things were firing in both movies and TV, and everyone was telling me how well it was going.”

"And I was really unhappy.

"I then had to grapple with why? What's off about this equation?

"I think the thing that I was confronted with is that it's really great to make the decision of 'f*** it, I do what I want,' but unfortunately there's a system of permission in place where people will go, 'We don’t give a s*** [what you want to do].' Like, 'Good for you, man.'"

As such, when deciding to do what he wanted, the Sex Tape actor found that he had to jump through hoops to make it work, while his creative freedom was limited.

He advised that 'it’s about summoning the will to say, “OK, s***, I have an idea and I believe in it and it won’t leave me alone and now I’m going to do the three or four years of fighting through all the permissions and pushing the boulder up the hill'.

Even though the Forgetting Sarah Marshall writer found it difficult to be surrounded by restraints, he fought his way through the final seasons of How I Met Your Mother, which left him feeling lost.

"After How I Met Your Mother ended, I didn’t know what I wanted to do next. I really wondered if I was actually good enough to do drama," he recalled.

"I took a movie called The End of the Tour to play David Foster Wallace. The degree of difficulty of it not looking like a Saturday Night Live sketch, when you get the glasses and the bandanna and you’re saying the lines, felt so high," he explained.

“I literally just played in my head, ‘What would Edward Norton do?' I got a dialect coach and I did all these things that I heard you do if you’re a real actor. But man, I was scared."

Even after feeling lost and confined during the end of his CBS sitcom hit, Segel shared that he would be up for reprising his role on the show's spinoff How I Met Your Father.

He told Entertainment Tonight that he would 'do anything' for the spinoff's creators, as they changed his life.