Deoxygenated blood comes into the right atrium via the superior vena cava.
Occupy yourself with activities or just drink water
You didn't really provide us with any options? It must be noted that generally, the structure of the skeletal system also dictates its function. With that I mean that having bones and a skeletal system enables us to move more efficiently and to have the pose which we have.
The brain gets used to you taking the drug. Some drugs will affect your neurotransmitters, or messages that get sent to your brain that regulates how we think or feel. You will eventually become dependent on the drug so if you stop you might feel sick or go through "withdrawal". Which people dont want to go through so they will continue to take the drug.