The advice given by Clayton is the best you can get, actually. Although I would add that you’ve got to focus on everything else rather than the tube being there. Find some distraction during the shower. For me, it was just the simple sensation of taking one. I would just do my things, get clean very methodically, and if I was too rough I would just take a break, let the water run over me for a while and concentrate on that and then get back to whatever there was to be done. And after being done with it, I usually treated myself with taking a few minutes of just letting the water flow. After a rough start, this method made me love showers when having a tube in. It was one of the few really pleasurable things I was able to do while being catetherized..
Hang in there, and remember that better days are coming. I’m 5 weeks post-op, the flow is great and uncomparable to anything I’ve ever experienced. Still forbidden to do some things – be sure to ask your doctor about ANYTHING – but slowly getting better and better. It takes one day at a time. Good luck!