Right. So now that we know we must be virtuous to be happy, I should probably tell you what virtue is. There are two kinds of virtue: intellectual virtues and moral virtues. They work exactly like you'd think - we're taught intellectual virtues, and we learn moral virtues by doing, through practice. We absolutely must train ourselves to be virtuous. Think of all the bullshit sayings we have about courage: neat, tidy little aphorisms that are supposed to explain a lifetime of learning in a single sentence - fuck those. I'm sure you can quote dozens of those about what courage is, and how to be brave - knowing about courage doesn't make you courageous any more than knowing about flight makes you a goddamn Eagle. The question is, when you're up against the wall and things look bad, do you have the stones to figure out what's right, and do it? That shit takes work. No one gets to be born a hero.
There are no hard and fast rules for virtue that you have to memorize, no table you can consult to determine what the right action is. How could there be? There'd have to be a rule for every single conceivable situation. I... I don't have time for that shit. I can't sit here and think, "Should a guy fight an enemy soldier who is way bigger? What if there are three soldiers who all look kinda tired? What if there are four soldiers on elephants, but the guy is on a flying narwhal? What then?" Virtues aren't rules you learn to follow, they're the mean between excess and deficiency, too much and too little. If some punk kid is robbing an old lady and you don't step up and stop him, you're probably a bit of a pussy, deficient in courage. If you've ever thought, "Bruce Lee and eighty clones? Fuckin' bring 'em on!" you should, y'know, maybe reconsider, because that's excessively aggressive, some might even say foolhardy. You're going to get the piss beat out of you. Where is the line in between? That's what you have to figure out.
In the process, you should probably master pleasure and pain. Pleasure isn't the same as happiness, and it isn't some pleasant riverboat cruise you can coast down on the way to happiness. That shortcut ends at a bar, drowning your sorrows in alcohol because it just feels so much better to be dead inside. That's not virtue now, is it? You have to dig the trenches of that river yourself and learn to direct your pleasure, so that you get that sweet twinge of quiet, personal victory when you say, "No thanks, I'm good" and you know it's the right thing to do.
Of course, sometimes bros accidentally do the right thing - when you point it out they're like, "Oh... oh! Yeah, yeah I guess that was kind of awesome, wasn't it?" Or else they try to play it off like, "Thanks man, I totally meant to save that dying kid by shooting him directly in the cancer from 800 feet away while blindfolded. I'm a hero!" So here's how you can tell when those bros are fucking faking it, and who really is virtuous. First of all, a virtuous man always knows he's doing the right thing. He's never surprised by how awesome he is. Second, he always does the virtuous thing because it's the virtuous thing. So you can't say, "Yeah, I saved the drowning baby, and obviously it was the right thing to do, but really, I did it because he had my sunglasses in his hand when he went under, and those are fucking expensive sunglasses." Third, and most importantly, he has to act from a disposition to do the right thing. He has to be constantly inclined to do the right thing, in an unchanging way. Virtuous bros are never like, "Yeah, I helped that injured guy up the stairs, because it was the right thing to do, but I don't know what came over me. I actually fucking hate him."
Virtue isn't some temporary feeling that washes over us from time to time and compels us to do the right thing; you never wake up feeling virtuous. We all get pissed off sometimes; that's not a bad thing. It only gets bad when we don't handle that shit properly. We get praised and blamed for how we handle feelings, not which ones we have. Virtue isn't an ability we have, either. We all could be virtuous - no what gives a shit about what you could do. No one is like, "Mike is such a great person - he totally has enough time and money to feed his children, and he's capable of so much love." Big fucking deal; but if Mike doesn't follow through, he's still a dick. If Mike is a great person, it's because he does feed his children and because he shows them so much love. Just because you're capable of generosity doesn't make you generous.
Virtue is a disposition, a tendency to do the right thing, to find the middle road between two opposite extremes; that's what we have to develop. "They" say every time you do something it gets easier, except I was the first one to say it, so suck it, Aesop. And I'm right; you have to get to the point at which doing the right thing is a fucking habit, not something you agonize over. If you have to talk yourself into not drinking too much, you're not temperate yet. But keep going! Eventually, you'll know you should stop, and you just will, because it's the virtuous thing.
Some extremes are easier to fall into than others - holy shit, remember that kid who discovered sarcasm in, like, third grade, and didn't say a straightforward thing for a whole year? We fucking hated that kid, unless we were that kid. Sarcasm has a time and a place, you know? And 'good-humored' is a mean between 'too serious' and 'fucking assclown'. But it's easy to be an assclown when you first discover something kind of funny; way easier to be that than to be a humorless suckhole. Eventually though, that kid got his shit together, or else we all stopped talking to him, so he learned real fast. Now, he's probably an alright guy.
So, look. To grow in virtue, just follow these steps: first, avoid the far away mean. Don't play it safe, or you'll never fucking learn; don't be afraid to be an over-exuberant dick for a month until you learn where the mean is on courage. That's better than spending your whole life cowering, afraid of being too bold. Second, pay the fuck attention. You don't get virtuous on accident; learn what mistakes you make and then make a point to correct them. Third, and most importantly, don't let pleasure get in your way. Seriously, being virtuous is a rational exercise. You should get pleasure from being rational, but that's just another effect like virtue, not an intermediate cause. So, you know, use your brain, kids, and don't worry about being perfect; this is a lifelong exercise here. Just be excellent.
You can find the complete Nicomachean Ethics online at Wikisource.
But if you want a paper copy, they're relatively cheap: Nicomachean Ethics on Amazon.com