Thank you, Matt. Interesting. May I express a slightly divergent view?
My issue is that in my working life I'm hemmed in by, and knocked over the head with, so-called SMART targets. Everything we do has to be forced into this framework, whether or not it is appropriate, and it leads to the mindset that if an activity or task is not explicitly measurable, then it is not valuable. It's not a mode of thinking I wish to bring into my personal life, as if every aspiration can be pigeonholed into the structure of a business operation.
Define goals too much, and you make it much easier to feel you've failed. My hobby and main form of relaxation/de-stressing is guitar playing, and I'm in a constant and pleasurable process of learning. If I SMART-ise that, say I set myself the goal of learning a certain passage or song in a week, and then I don't manage that, then there is a feeling of failure, non-achievement and the real danger, what with me being depressive, somewhat impulsive and emotional, of putting down the instrument for good or for a long period of thime. This has happened before.
"I can't do that, I'll never do that. I'm no good. Anyone else could do this, but not me. Oh no. because I'm Pete and I'm defective...."
Maybe this is a trivial illustration of what I'm saying, but I'd counsel caution when considering systematising one's goals and aspirations. Especially for us depressed-type of folks, it can backfire. It can have the opposite effect to motivation.