Rooney was sent off after kicking Montenegro defender Miodrag Dzudovic in last month's Euro 2012 qualifier in Podgorica which led to a three-match suspension from UEFA, effectively ruling him out of the tournament unless England qualify for the knockout stage.
The English FA will announce on Friday if it plans to appeal against UEFA's decision, while Rooney said he understood if coach Fabio Capello left him out of the squad for the finals.
"It was stupid of me and I regretted it as soon as I did it," the 26-year-old told British media.
"There was no tackle beforehand and I didn't think 'I'm going to beat him' - it just happened.
"Obviously, it's devastating for me but it's something that's my own fault, so I can't really complain. It's no excuse, but I still feel the punishment is a bit harsh. I'm disappointed with it.
"All the details we have been waiting on have come through, so we'll be making a decision as to whether we will be appealing. Even if it's reduced by one game, it will be a bonus for me."
He said he had no idea why he acted as he did. England, who were winning 2-1 at the time, went on to draw 2-2 with Montenegro to secure their place in the finals.
"I honestly don't know why. It was just one of those moments which I live to regret now," he said. "It just happened. I can't explain it.
"I want to be there and be part of the team but I'll understand if I am not in the next squad because I'll be missing the first three games and he [Capello] has to look at other players, I understand that."
Capello watched Rooney shine in midfield for Manchester United in their 2-0 win over Otelul Galati in the Champions League on Wednesday but Rooney is expected to return to his usual position in attack for Saturday's Premier League match against Sunderland.
"It's probably a role I could enjoy in the future when I've lost a bit of pace," he said. "I played there as a young lad, I understand the role."
