Both by necessity. When I was a kid, the teachers thought it was a good idea to force everyone to be right handed, even though I was definitely a lefty. So lefty is natural to me, but I was forced to learn to be a righty too.
I mainly eat and write left-handed and do nearly everything else right-handed, although I switch off depending on what it is and how tired I am. The sleepier I get, the more uncoordinated my right hand gets.