Nature offers consolation and larger order. Though gardening design is very long term, the actual practice of horticulture is very immediate, with concrete physical progress that's very helpful. In the meantime, my mind can go off and think about anything it wants. Gardening is also useful in thinking about HIV because making and keeping a garden is about orchestrating death and dying. All plants have a life span.
Annuals are purely seasonal, but perennials die at different rates.
I have to understand how and when plants die and what to do to make sure that the garden as a whole continues. I've got to accommodate all that dying. There's constantly going to be dying. I have to think in terms of decades. I might die before it does.