It's not going to hurt the machine, in and of itself.
With that said, it's better to figure out what's happening. First off.. What machine do you have exactly? What specs?
While it's not been my own personal experience with Yosemite, others have reported it being fairly buggy for them - especially wifi issues. It could be software, or it could be related to your router. Same goes for the lag...
We need to know what your working with.