Your ShowerThoughts Board should stick to your shower for a long time. Eventually it will fall. The inexorable pull of gravity takes us all.
If your Board keeps falling there's a few things to try:
1. Make sure the sticking surface is not porous. Glass and tile work. Rock, metals, and porous surfaces don't.
2. Make sure to thoroughly clean the surface and suction cup. Let them both dry completely before sticking the suction cup to the wall.
3. If steps 1-2 don't work, try step 2 again and then rubbing a bit of Vaseline into the suction cup.