My wireless network connection gets lost frequently (OS X 10.10.2)
I have struggled with my own connection dropping intermittently (more often, just becoming very slow/weak for periods of time).  The problem for me seems to be that I chose a spot in my house that has poor Wifi signal, perhaps due to the configuration of walls, the configuration of metal in my house construction, and so on.  If I move my computer a meter or two to the left, the problems go away.

Also, the problems are much worse for a Mac laptop whose lid is closed.  The antenna is located in the hinge, and with the lid closed, the antenna's ability to receive signal is reduced by half.

I don't know exactly why wireless signal strength changes over time, causing intermittent problems.  Could be the use of electronic appliances in my house or someone else's.  Could even be solar radiation changing when clouds go by.  Best thing to do is get your router and computer jointly located so that the signal strength is generally strong - then fluctuations won't cause you to get accidentally dropped.

To check out your wireless signal strength and see how it varies when you move your machine around the house, follow this link:

http://letstalk-tech.com/how-to-access-the-wifi-scanner-in-mac-os-x-yosemite/