@roger,
roger wrote:
Buy a grab bar and install it before you try.
I have a brand new (never been used) shower chair/porta-potty from when I had my surgery a couple years ago.
You are more than welcome to borrow it to give yourself a soft place to land in the shower, should you need it. It will also allow you to take unassisted showers while sitting down (until you gather the endurance for a fully unassisted stand-up shower.
If you want me to bring it over, just say the word. It is out in the garage gathering dust.