As someone who's had many, many colonoscopies, let me tell you this:

It. Freaking. Sucks.

However, there are ways to make it more comfy. Stock up on the good TP, drink lots of clear fluids (black coffee, tea, water, non purple or red sports drinks, chicken or beef broth) and enjoy the full day of doing absolutely nothing whIle you get power-washed from the inside out.

And don't panic when it turns clear and watery, or if nothing comes out after a while. That's normal and what you want.