This is a question I've been thinking a lot about lately, due to circumstances in my social circle.
I think there are different types of infidelity. There are the serial philanderers (of both sexes) who simply want their cake and to eat it and don't care who gets hurt in the process, although they may lie and cry crocodile tears when caught. Then there are those who just don't possess enough self-awareness to realise when they're treading on dangerous ground (these are the types to whom it 'just happened'). Some of these will have made a genuine mistake and be full of genuine remorse and wil change. Others won't, either because they're not really suited to monogamy or because they're a bit dim.
In all these cases, I'm talking about mature people in marriages/long-term cohabiting relationships, in which the act of infidelity is affecting the future of the relationship.
What I'm less clear on is where maturity fits in on this. Is it possible, for example, for someone to have cheated on someone in a serious (but not cohabiting) relationship while in their early 20s but be trustworthy in a completely new relationship years down the line?
I tend to be of the opinion that while everyone can make mistakes, learn from them, change and move on, most people just don't. They repeat the same patterns of behaviour ad nauseam. Maybe I'm just a cynical old bat.
I'm interested in all different opinions on this, but if it's not too personal I'd quite like people to state if their opinion is coloured by personal involvement (which in no way makes their POV less valid).