It is a moral defence though, it's called "mitigating circumstances". If it's the first offence, if you can convince a judge that it was an out-of-character lack of judgement, that you have regrets, and assuming you didn't actually crash, then he will show leniency. So yes, it's a legal defence.

As for a moral defence... ask yourself, would you find it easier to forgive someone who wronged you as a result of a momentry lack of judgement, compared to someone who coldly set out to wrong you?

"Sorry I fucked up" is a moral defence if it's sincere.