The Leicester City midfielder won his only cap three years ago but always believed he could get back into the squad, even if he was not involved in any of the qualifiers.
"There were times that I’d been playing well and not been selected but it’s about having the right mindset and staying hungry to try and achieve," Maddison told a news conference on Wednesday.
"We’ve seen in the past that (England manager) Gareth (Southgate) has brought players back if they are in form and thankfully that was me for this tournament."
Maddison was in Leicester manager Brendan Rodgers’s office on the day of the squad announcement last week.
"He asked me if I heard anything and I hadn't at that point. He was just being a good manager and putting a close arm around me if I didn't get the call, talking about staying motivated and then enjoying the break.
"But when I got back down to the change room I saw I had a missed call from Gareth Southgate. My heart started beating and I called him back and he gave me the good news."
Now Maddison is relishing the World Cup experience
"Every moment at the minute is almost like pinch me moment," he said. "It sounds really cliched but just getting on the plane and then getting off the plane, seeing the reception we've got from locals, it's all a bit surreal. It’s my first major tournament so I'm just trying to take it all in."
Maddison had a scare at the weekend when he went off with a knee injury soon after scoring early at West Ham United in Leicester's 2-0 victory.
But a scan revealed no serious problem.
"I will have to do a little work with physios here to get up to speed," he added.
England open their Group B campaign against Iran on Monday.
"England in recent tournaments like Russia and the Euros have been brilliant and coming back into the squad you get the same feeling of togetherness," Maddison said.
