Every metaphor for a garden overlays onto life (and vice versa) because a garden is life. One of those lessons is that you are not a god... that no matter how well things are going, things can and will go wrong, and sometimes there is nothing you can do to stop them from happening... because you are not in charge. Nature is.
This:

is mosaic virus. Nearly every plant species is susceptable to some variation of it. There is no treatment or prevention. It is carried in seeds and spread by bugs, tools, hands, direct leaf contact, even the wind. As a steward of nature, the only interventions are removing the sick plants from the garden, keeping bugs at bay, and practicing sanitary tending methods.
I experienced my first mass garden loss from mosaic 3 years ago, when I planted tobacco seeds acquired a random ebay seller. I watched as half my garden slowly, but quickly, died. Every morning, I could see how it was spreading from plant to plant. Everyday my garden became a little less vibrant. I didn't know what was wrong then, but I do now.
It seems that this year, I must have acquired some carrier green bean seeds from a different, unfamiliar seller. My beans are dying. There is a high probability that most of my garden will die very soon. I will remove the sick plants as they appear and I will tend my garden cleanly, but pollinators are going to pollinate and the wind is going to blow... and there is nothing else I can do but hope that some things make it through.