1. It's better to target an interesting constellation than one specific star. If you're pushing yourself reasonably hard, you're working close to the limits of your ability, and so there's some chance you will fail. If you go all out to hit an ambitious goal and don't succeed, you're likely to feel burnout [1]. This is much less likely if you make moves in the direction of an interesting area using a cluster of subgoals instead. This diversifies your risk, plus it's easier to adjust as you move in that direction and learn more. (For people in ML there's some clear parallels with the gradient descent process)
2. A twenty minute walk in the park with no music or media makes all kinds of useful stuff naturally fall out of your brain, and you get some light exercise and sunlight / vitamin D at the same time - which also helps improve your mood and flush out anxiety etc.