Why is hard to make important decisions?

It's obvious that we are all faced with decisions which may one day effect our future or lifestyle! I have been dealing with a great deal of stress for the past two months. My mom was diagnosed with cancer and my job assigned me to another position. Although it is my desire to take two classes, the load is difficult and somewhat overwhelming. This has lead to a great deal of stress, restless nights and mood swings. I have prayed over this situation and have come to realize that I may be taking on two many things at one time. Dropping one of my classes seem to be the ideal thing to do, but on the other hand, I fear that I may regret it in the future. Is it normal to feel this way?