I don't like your previous comment because it can mislead people into doing something irresponsible even when it doesn't feel good because they think they should only be responsible for themselves and not others.
Example: What is a more desirable situation?
A persons taking responsibility for a child out of a deep feeling that it is good of a person feeling forced into taking care of a child because of cultural pressures? (Arguably) The child of person 2 is better off when someone is found that feels natural responsibility for him/her.
Luckily most parents feel strong responsibility for the well being of their offspring. For those that don't, we have adoption agencies and other methods to help. Generally our society believes it to be more moral that people can give their child away than to force them into a responsibility they don't want (or know they can't handle). So we already believe, even for our own children, that responsibility is yours to take, not something you have by default and needs to be forced upon you. Forced responsibility is not love, it is anti-love, it will lead to sick relationships.
So to come back to the original post: Being adults is about taking responsibility, not about complying to some culture enforce role model that is responsible for others. You can not be forced into taking responsibility (meaning you don't somehow have it) but if you don't take it, you'll end up nowhere (you'll be a homeless person or in jail.)
A certain statement like "You certainly are not responsible for other people.", is misleading and unhelpful because it suggests people who are tempted by relationships outside the home should go ahead and pursue them, even if it means feeling bad for being irresponsible towards your children and family.
Your point is you are being responsible because it makes you feel good, taking these feelings for granted. Yes, nature gives them to us to begin with, but they must also be nurtured. Between the good dog and the evil wolf in all our hearts, the one that wins is the one we feed.
For me that falls under taking responsibility for my own life. If I were to be constantly tempted it would be a signal something is wrong. I'd discuss this with my partner. Perhaps we should break up. The alternative is staying with him/her out of pity. Pity is not love, staying with someone out of pity is worse than leaving them imo. If my partner was constantly tempted but staying with me out of pity it would be the ultimate insult. I want my partner to be with me out of pure self-interest, because I'm the best choice, her favorite human being, her ultimate partner, the best she can get. I don't want to be a compromise.
I think that there is even a case to be made that leaving while you have children is better for them than keeping them in an unhappy marriage. You are certainly not giving a good show of what love is all about.
I do agree about the feeding, you certainly have the power to feed and deprive certain feelings.
Okay!
You should not live for other people and other people do not have to live for you. For me being an adult is more about that balance.