Competitiveness is almost a lost art. Where do you draw the line between having fun and wanting to win? Or balance, rather...
Expecting all outcomes is one way. In a tournament, for example, where you have no idea who your opponents are or their strengths, you could go with your experience and be the strongest, and you could as well be the weakest and get tossed around. There is no reason not to play the best you can. If you do know the strength of your opponents, I guess that is where loving what you do comes in.
There will be high highs and low lows, and the only thing that will keep you from calling it quits when it gets tough is knowing that there is nothing else in the world that will give you that much satisfaction, so you stick to it. You love it, so you stay until you get good.
Maybe some people are not down to metaphorically "kill" themselves during training and the actual activity. 5 years of extreme grinding and being the best, leaving on a high, is debatably better than 10 years of just-above-average performance. You will leave the activity after completely giving yourself, but on a high, and who is to say you will not find another activity you will love as much as you did the one before?