The injury-prone 22-year-old, who broke his foot in March, said he had been desperate to get back to first team football, fearing that if he was not playing England manager Roy Hodgson might not include him in the party for Brazil.
"I was panicking a bit about the squad, I wanted to be in it," Wilshere told the Guardian.
"I thought I was ready but he said: 'No, you're not. You need to train alone if you are to have a good World Cup. You need a good fitness base and to be right in every aspect.'
"That is what I am now."
Wilshere only managed two more matches for Arsenal after breaking the bone in his foot playing against Denmark in March, a match that marked only his 15th appearance for England over the four years since he made his debut as an 18 year old.
His frequent injuries have led some critics to wonder whether he will ever fulfil the potential he showed as a teenager, a question mark Wilshere is convinced he can remove if given a chance in Brazil.
"I think a good World Cup can erase a lot of doubts," Wilshere added.
"It is about the team and, if the side has a good World Cup, you are going to look good as a player.
"It's up to the manager if I play but I'd like to think if I'm on the pitch I'll have a successful World Cup - having an impact, playing well and keeping the ball.
"If someone had told me four years ago I would be going to a World Cup now, I would have been happy with 15 caps and this chance.
"To have played only that number of games is disappointing but I have to look to the future and hopefully I can contribute."
With both his appearances for Arsenal since the injury coming as a substitute - including a cameo in the FA Cup final win over Hull - Wilshere knows he has his work cut out to prove to Hodgson that he is match fit before England's opener against Italy in Manaus on June 14.
"I just wanted to be here," he said.
"I would have been devastated to have missed out and I knew the work I had to put in. If I got here, I could prove to the manager I'm ready."
- Sports & Recreation
- Roy Hodgson