Here we are in July with the heat index well over 100 degrees daily. Even if you get up at 6 am to go out to the garden like we do, it is already 80 degrees and too hot to do much in the way of digging.
Imagine how your garden plants are doing in the heat and mostly dry conditions.
This is not the time to dig plants, prune plants, or divide them.
The best, simple rule of thumb is to do all of those things right after flowering, in the cooler temperatures of the fall or in late-winter/early spring just as the plants are breaking dormancy.
If you dig up the roots of a plant now or even give it a hard pruning, you stand the chance of losing it because it is so hard for them to recover in summer's conditions.
So, just remember (memorize) 'prune after bloom' and remember that that includes any other action that disrupts your plants at the roots.
For now, just be compassionate: mulch the roots so they stay as cool as possible and deep water very early in the morning so the leaves have all day to dry off before night fall.
Simple and effective, plus saves you from doing too much demanding work in the heat.