The past can be a deceptive thing. In life we believe that because we see can how events unfolded, and the conditions, and decisions leading up to them, that we can determine whether a 'mistake' was made based on whether or not the outcome was desirable or not. In a world with innumerable variables that affect events, and where our sample size consists of precisely 1 (the past that actually happened, rather than the billions of other pasts that might have been), this is a lot less true than people naturally tend to think. In the case of a controlled scientific experiment, with a limited number of variables, and after a large number of trials, definitive or near-definitive conclusions can often be drawn about the isolated variables in question. However when looking at decisions in life, whether they be on a personal or national level, the variables are often much more difficult to isolate, and we only have a single sample to work with.
We are conditioned to learn from our mistakes from a very young age. When we touch a hot stove, it hurts, and we know to not to touch a hot stove again. The cause-effect in a scenario such as this is very direct and obvious. In a case like this, the results are much more like a scientific experiment; there's a single isolated variable (does this event cause pain?), and there are hundred of thousands of iterations, all with the same result (yep, pain occurs.) So in this sense, results-oriented thinking is not always flawed. Results can be illuminating, when we know how to interpret them.
However, because this kind of thinking is useful on this level, too often we apply it to areas where it isn't really useful or applicable. For example, say you have a choice of two career paths. You choose one path, and after 10 years in that career you are reasonably content and satisfied with your life. Does that mean you made the correct, or optimal, choice in choosing the path that you did? No, because you have nothing to compare against. Had you chosen the other path you may have been even more happy with your life and circumstances. There is no way to know.
There are a small number of variables that leaders of nations take into account when deciding whether to wage war, but there are near infinite numbers of variables that can affect the outcome of a war, one way or another. Many people hold it as self-evident that Vietnam or Iraq were 'mistakes' because of how they turned out. Though the negative outcomes may outweigh the possible negative outcomes of not having gone to war, we have no way to know for certain (though we can make some reasonable assumptions.) Not to mention the fact that the undesirable outcomes could have been due to decisions made about how to wage the respective wars, not whether to wage them at all.
In short, undesirable outcomes are not always the result of poor decisions, and desirable outcomes are not always the result of wise decisions.
In becoming a successful poker player you have to train against results-oriented thinking. If you let the results of a single trial, in which there is an enormous amount of luck involved, affect your decision-making then you are going to start making bad decisions. Short term results tell you nothing. You could make perfect decisions on 10 straight hands and lose them all. Conversely you could make bad decisions on 10 straight hands and win them all. Because there is randomness and luck involved (as there is with life), you have to focus on making the optimal decision, and not worry about the short-term results. The difference between poker and life in this sense is that if you continue making better decisions than your opponents in poker, then it is a mathematical certainty that you will win in the long term. Where in many areas of life you could make good decisions (given the available information at the time) that have unforseen consequences, both short and long term. Still, your chances of succeeding in life are obviously much better if you make wise, informed decisions that are more likely to have desirable outcomes. Though those outcomes are not guaranteed.