Stress

When your job involves being surrounded by sparkly rocks and mushy engaged couples, there's not much stress.

 
Oops, there goes my pension. (Source)

Unless, of course, you accidentally take too much off a diamond while cutting it for a setting, decreasing the value by thousands and thousands of dollars. Or if you botch a big appraisal for your boss and risk losing your job if he finds out.

Not. Much. Stress.

Other than those scenarios—which would be pretty stressful—gemologists don't face a lot of day-to-day stress. You might have to deal with a crabby customer or some rush-hour traffic, especially if you're making regular trips to New York's Diamond District for a client pickup/drop off, but that's the sort of stress that pretty much everybody faces. That's not so bad.