Allot of fields I have flown at are setup for left hand traffic patterns, however I have flown at many fields which are both left and right patterns. As an example, a few times while flying in LA at Sepulveda Basin, late afternoon winds would shift and the pattern would change from left to right. It took a bit to get used to because all day I was flying a left pattern and then I had to change to a right but it was not unbearable. For me the left hand pattern was comfortable because I was used to it, muscle memory if you will. It's really all about practicing and getting used to both ways building up your experience, If not at the flying field, practicing at home on the flight sim.
Steve