One this should not be posted on this section this is a welcome area. But on your questions. tehir or things behind the viel that can be of harm. Abnd their are ways to keep from such or prevent it. If you believe in the three fold law then yes. I personaly do not follow such an ideal but it is often followed by others on this site and round the world.
It is my opinion that with magic, as with anything else, there is an equal and opposite reaction. It is basic physics. Before doing anything, you must understand all of the possible repercussions, and consider the entire situation logically. If you throw a punch, you start a fight. You push something, it moves, falls over, or pushes back. Etc.
Using energy has its own consequences. It can leave you light headed, dizzy, nauseous, etc. It all depends on you, what energies you use, how balanced you are, if you are grounded, etc.