It's better to fail fast than to waste 5 years getting a PhD you don't really need. I've had a lot of professors who started out pursuing theoretical physics in

It's better to fail fast than to waste 5 years getting a PhD you don't really need. I've had a lot of professors who started out pursuing theoretical physics in grad school, but quickly switched to experimental physics after realizing that they were simply not the right material for theory. I was always surprised to hear it, because I regarded those professors as very bright. It is very humbling.