It's something I used to do a lot as kid, but less so now as an adult. It's simple, just hang upside down off a bed or sofa or simply lie on your back on the floor. Then let your imagination run riot as you think what it would be like if the ceiling was the floor.
I know you're probably thinking I'm a little (or a lot) crazy at this point but just try it.
Sometimes, as with all things in life, it can be useful to look at things from a different perspective.
Come walk with me on the ceiling.