I usually work with my laptop and always shut it down for studying or doing other works (for half hour to two hours, about 6 times/day).
Is this harmful?
Generally there is no exact answer however its best to not turn the laptop off and back on a lot if it can be avoided. Shutting down the computer also uses power so for short periods (many hours) using Sleep or better Hibernate would save power. Also allowing electronices to cool and heat frequently is not the best for their long term use and lifespan.
Using the Power Plans properly along with good Sleep and Hibernation settings, which are dependent on how you use the computer, will get the best performance and lifespan however there are no exact answers. Those which seem to be best for how you use the system will probably also be best in the long run. If you "could" set with the magic settings that would optimize the machines functions and life but then use the machine in a different pattern, which we all would, then in fact you would actually get less use and lifespan than setting to your use patterns.
One thing that many forget is that turning the screen off can also save power when you will be away a short while and would not want to turn the computer off. This will save some power over using a screensaver but can be hard to remember and does not save a lot.
Best to refer to your System maker's Support, their on-line documentation, and their forums about your model.
Shutting down your computer is not harmful. The reason people use sleep is because it's faster than having to wait for the computer to boot, and it keeps everything as you left it. But even then, you have to reboot or shutdown your computer sometimes. So the only thing wrong with always shutting down your computer is the time you'll lose waiting for it to boot.