Chess is an activity that consistently throws up the same problem: what is my best move in the current position? I have noticed an unstable dynamic. Firstly, I try to continue with my tactical plan (Apart from in the opening, I always pretend to myself that I have one. Note that moving your pieces to good squares is NOT a tactical plan.) Secondly, I look at all (well, some, anyway) of the moves that are possible in the new position and try to see where they lead. Ideally, the second approach should do little more than confirm that the first is still on track. Instead, I often find that I have missed moves (both my opponent's and mine) and so I re-evaluate from scratch. "Missing moves" includes more than simply not considering a viable move; it includes missing that the given move leads to possibilities that need to be explored further. In other words, I might consider the move but dismiss it too early.
If you are Kasparov or play people far below your standard then you might get few surprises, but if you play people of similar skill then you will often be surprised by how a position develops. Why is this so? I guess the answer is the same as the reason why we love chess. Because it is challenging and unpredictable. No-one, not even Deep Blue (RIP 1997), can work it out from beginning to end.
As for me, I keep getting unpleasant surprises. The thing I am reminded of, painfully often, is that I spend far too little effort on working out my opponent's tactics. My new resolution is to spend 60% of my effort on thinking for my opponent and 40% on thinking for me. The idea is to arrive at a 50/50 balance eventually.
Yet this approach is based on an illusion. Ultimately, there is no distinction between "thinking for the opponent" and "thinking for myself". Why? Because whatever line of moves I explore, it has to include moves for both sides. Not only that, but it should contain the best moves for both sides. What does that mean? It means that I need to consider the best tactics and strategy for both sides as I explore each variation. There is no point in thinking only of my strategy and tactics and ignoring what my opponent wants to do.
What I am attempting to elucidate here is that a chess game cannot be seen in terms of, "Here is what I want to do, let's see what he can do to stop me." It is equally about, "Here is what he wants to do, let's see what I can do to stop him." In fact, the actual game is a mix of these two patterns inextricably meshed. There is only one game, not my game and his.
Somehow, I find this hard to understand and even harder to apply. I have a resistance to thinking really actively about what my opponent should do.