Author's note: This is the first in what I suppose might be a series of posts with respect to things I learned from playing traditional games competitively that I think might have broader applications. I write this as a private individual, not on behalf of CFAR or any other organization.
Traditional games - card games, board games, miniatures, etc. are a lot of fun, and I've played several of them at quite a competitive level. 
The #1 piece of advice that I can give if you want to get better at these games - a piece of advice that applies across essentially every game or sport I've played and a lot of "real world" stuff as well - is "if you want to win, stop conceding."
On the surface that doesn't sound super deep or interesting, but there's more to it than the obvious meaning - not all concedes are formal resignations, and indeed the ones that aren't are often more important.
Some time ago I read a book - either "The Inner Game of Tennis" or "Bonds that Make Us Free" or maybe both - that taught me that very many people concede games well before they need to be over, either because they incorrectly estimate their chances or because they make a mental motion away from trying to win and towards trying to make excuses for losing.
Here are some examples of what excuse-making thoughts might sound like:
- "The dice are against me, there's nothing I can do."
- "I didn't get a good night's sleep or eat breakfast this morning, otherwise I would be winning - I just can't focus."
- "This guy's bad but he got lucky." 
- "This guy's way better than me, I shouldn't even be matched up against him." 
- "I don't know how she even got this far ahead, there must be some bug."
- "This is pointless, why play it out?"
- "This is just for fun anyway, I've basically lost, may as well wind things down."
Once you have moved from trying to win and towards trying to excuse losing, you have more or less already lost. Sometimes an opponent might snatch defeat from the jaws of victory, but that's rare. Most of the time, assuming you've lost is the same as actually losing, it just takes longer.
If you want to get better, stop it. Force yourself to keep playing and keep looking for outs. Learn to recognize these mental patterns and suppress them. Don't concede games unless there's nothing you can do anymore. Fight until the bitter end.
That's a real 'if', because if you don't want to get better I certainly don't recommend doing this! There is a sense in which it is viscerally unpleasant to force yourself to be in a losing position, desperately scrabbling for anything that can get you out.
When you get in that position and escape, it feels great - but there are also going to be times when you don't escape, you struggle for ten or fifteen or thirty minutes but still lose, the whole thing feels bad, and you might wish you had conceded in the first place. If you aren't prepared to face that, maybe don't bother.
But what I've found is that a practice of facing the negative thoughts and pushing through seems to have been quite beneficial to me across a wide range of games and areas, so I would give serious thought to the notion that - at least in areas that you care about and want to be better at - you should consider this approach.
A few days before writing this, I played a card game where around two to five times throughout the course of an ~hour-long game I was struck by thoughts along the lines of "Wow, my position is horrible. I've been really unlucky. I should concede."
I didn't concede, and I won the game. This is not a particularly unusual experience to have once you acquire the inclination and ability to push through.
 For calibration:
At various times I have been world #1 by Elo rating at a few different games I've played (not all at the same time!). I came in third at the World Championships of L5R this year despite being out of practice (though to be fair I had some good luck).
I have flown to a card game tournament in another state in large part because I calculated I was likely to win enough in prizes that I would net gain money from the trip; I haven't eBayed all the promotional items I won yet but I believe I indeed made hundreds of dollars from that venture.
I don't say this to boast but rather to give an indication of where I am coming from. In order to "deflate the sails" a bit, I should say that I do not make a career out of gaming and I don't play poker or Magic: the Gathering competitively, which have a significantly higher level of play than most games I play; there are many people who are better at games than I am.
 This thought pattern is especially bad because it prevents you from learning from the game after the fact. Sure, some games do come down to luck in the end, but probably there were decisions you could have made prior to that that would influence the odds.
 A joke saying goes: "Anyone worse than me at this game is casual n00b trash. Anyone better than me at this game is a no-life tryhard." Neither of the thoughts in that dichotomy is very useful to have, even in their less straw forms.