Great points by doctorspock. Conserving or using energy at the right times is very important. Part of my point however was that on a local level you are not racing in a vacuum. Good racers know and play off the strenghts of other riders. Ride a few succesfull breaks and you will attract strong riders when you attack.
From a strategic viewpoint I think it is more difficult to race dependent on breaks in lower levels than in Cat 2 and up. In lower levels the field tends to be impatient, and will chase down pretty much anything that goes. In 4,5 races I don't so much see breaks, more field splits or selections. In higher levels there is a bit more patience in letting a little break develop, just to see what happens.
Based on this my observation has always been that to have success at lower levels you need to either be significantly stronger than 90% of the field, or develop a sprint. The outlook is pretty bleak for a moderatly strong TT type racer as a 4 or 5.