There is no mask, you simply have one personality.
Human personalities are very contradictory, and different facets show themselves at different times. For example, a good parent loves their kid right? But what if their kid disobeys? They must be punished sternly. Now where's that loving side? Not showing, the serious side is. The serious side isn't showing when you talk to people about your feelings though.
It's a sign of a healthy personality, the ability to behave properly as situations call for it.
Also, things like your job. If you get fired from KFC, has your personality changed? Not really, you're still the same person. So lists like that wouldn't apply unless we only did what we wanted all the time. In addition, we'd have to know what we wanted and many do not.