I'm not especially attentive to watering plants, although I know ample water improves my plants' chances of survival. If possible, I plant my divisions soon after a rain or when wet weather is forecast. Otherwise, the divided plants get a quart of water in their new hole to form a good bond with the soil. Sometimes a plant wilts with this stark regimen, only to send up new vegetation with the next good rain. Many plants seem to grow faster and flower prolifically when they're under some stress from frequent division.
Plants seek, above all else, to propagate.
When threatened, they concentrate on survival, pouring extra energy into producing more flowers for seed. I've seen daylilies, Shasta daisies, sedums, hostas, and phlox react this way in my garden. Of course, I don't ignore their needs completely. I have found that a spadeful of homemade booster mix helps a plant adapt to its new home. My recipe calls for roughly equal parts of leaf mold and manure, plus a bit of bonemeal.