Unless you're using a respirator with a charcoal filter canister, the mask does nothing but make you uncomfortable.
The risks depend entirely upon the finishes you're using. Most finishes are pretty safe to be around. The bigger issue is probably going to be your heightened sensitivity to smell. If it smells strongly, you'll probably want to avoid it.
You can also greatly minimize exposure by wearing vinyl gloves when you do your finishing. They're inexpensive to buy in bulk, and they make cleanup a lot easier for you as well. I especially use them when dealing with an oil based polyurethane, because the material can deposit a harsh abrasive layer on your skin that takes a couple of days to wear off.