I take full responsibility for whatever mistake I have made in the past, even if it's just a spelling mistake. For me, they are not something to regret but to accept. We all make mistakes; there is no such thing as a 'perfect person'. The good thing about mistakes is that they can teach us essential values that nobody else will.
Our class was recently assigned a group project to do in Science. My group decided to make the task so fancy that we couldn't complete it in time, thus getting a big, fat zero. I learnt that we should make things easy and beautiful simultaneously. Even though this error will probably affect my grade, it doesn't matter as long as I learnt something.