He needs to find out for himself that he's not missing anything...btw he IS missing a LOT.
Being Single and being in a relationship affect your lifestyle in different ways, and everyone should take time to enjoy both.
The man says that he's in a committed relationship, but that he's scared of the fact that he might miss the "single" experience. If you tell him that he is missing "a LOT" you're giving him encouragement for him to leave that relationship to live the single lifestyle that is completely overblown by the media.
It's easy to tell people they are missing the best part of being in their twenties, when in reality it's not all that it's been made up to be, as the only thing it really contributes to one's life is a false sense of accomplishment.
Here's another golden nugget for the grandparent: Everyone talks about the single lifestyle, but that's a lifestyle suited for a really small fraction of the people that supposedly tell you it's the next big thing. You need a boatload of social skills that a great percentage of people don't really have, you need to be sort of successful at the moment, you need to have a way with women (which is something that comes from a boatload of experience), and you really need to have at least a couple of friends that are living it large as well.
I've seen friends make this exact same statement, that they are missing out and that they think they should leave the relationship they have and try the single lifestyle. It always blows up in their faces. In contrast, the two friends I had that really lived this lifestyle at the same time I did both realized they where going down fast and now one is married and the other one is engaged.
If there is one advice I can give you GP. If you have a couple of friends that tell you it's the greatest thing ever, the threesomes, the challenges, the satisfaction of bedding that model, etc... realize one thing, for every one of those men, there are hundreds (if not thousands) that won't achieve the same experiences, and the one's that do generally burn out pretty quickly. If you were single, I'd tell you to try it out and see what happens, but you're not and it would be a mistake to try to live it up just because. If you're happy with your significant other, don't sweat it, it's a lifestyle not worth your while.
Hell most people that do live it up like this don't do it because of a life choice, they do it because it's the only thing they have ever known, and it's a thing that just happened. You can't artificially become a money spending ladies man just like that.
