Obvious statement: there seems to be a lot of variance within millennial individuals. Commenting on my own personal experience, there seems to be a massive spectrum of folk within my demographic. I was 15 when the millennium came along, so I'm probably in the middle (?) of it all.
Personally, I am a somewhat serious and boring person, because I'm an INTJ. I don't actually like interacting with other individuals all that much, so I ensure that said interactions are handled in ways which could be classed as... ahem, 'efficient'. It is very rare I come across another person with who I can connect on an intellectual level - and that's basically all I care about. Talk to me about whacky ideas or fuck off, basically. This is an area which I have to work on, because I'm probably missing out on the human side of life somewhat... but then I prioritise it so lowly that I can't even begin to fathom how it could ever be of benefit to me. Perhaps in time, eh?
I haven't ever been afraid of hard work. Years of abusing games like World of Warcraft mean that my brain has become wired to positive reinforcement type bullshit, which has lowered my focus (I'm working on it - but holy shit, pronounced issue is pronounced) but that aside, I'm always eager to get stuck in. When I'm on point with a project, I will work tirelessly into the wee hours to ensure everything is either perfect, or ready to be taken up the next day from a vantage point.
I don't have many hobbies, and I seldom indulge the ones I do. I'm very happy with life overall. I have a wife (ENTJ - also confirmed professionally) and two children. One is two years old, the other is three months old. Both are XX. I have a great job that, whilst the pay isn't great at the moment, the potential for growth is huge.
I'm nothing if not pulled in more than one direction, though.
Older generations (my wife is actually X!) I get along just fine with. It's people of my generation and younger who I tend to have issue with. SJWs for example. If ever a bunch of motherfuckers needed shooting...