Hales, who struggled in his debut Test series in South Africa, has seen the likes of Sam Robson score heavily.
"I knew openers would inevitably score runs and put pressure on - that was one of the cons of the decision," he said.
"But if I turned up with half a tank, I wouldn't be giving myself the best chance to cement that England spot."
The 27-year-old, who has been opening at international level in all three forms of the game, averaged 17 in the Tests as England beat the Proteas 2-1.
While many of his England team-mates were cleared to play at the beginning of the Championship season, Hales opted to sit out until Sunday's game against Yorkshire at Trent Bridge.
He is likely to play only twice before England name their squad for the first Test against Sri Lanka, which begins on 19 May.
In his absence, fellow England opener Robson scored a double century and a century for Middlesex against Warwickshire and Durham's Mark Stoneman reached three figures for Durham against Middlesex, while the likes of Ian Bell, James Vince, Adam Lyth and Varun Chopra have also been in the runs.
"In the best part of 24 months I hadn't had more than three weeks off cricket," Hales told BBC Radio 5 live sports extra.
"I was pretty knackered to be honest, probably more mentally tired. It was nice to switch off from the game.
"The most important thing was coming back with a full tank and the desire to score as many runs as I can. The break has 100% done that, so I have no regrets."
Hales, who played limited-overs internationals for England some five years before his Test debut, was selected as captain Alastair Cook's eighth opening partner in three years for the series in South Africa.
Although he only made 136 runs in eight innings, he said he felt at home at the highest level.
"South Africa didn't go to plan, but I didn't feel out of my depth," he said. "It was me making errors rather than thinking that I wasn't good enough.
"If I do carry on at Test level, it's up to me eliminate those mistakes."
England opener Alex Hales says he has no regrets over resting from Nottinghamshire's first two County Championship matches of the season.