Doug,
Try this for the next 2 weeks. On a service call or a small install that you would normally quote a T&M price for.
Use your experience to determine approx. how long it will take you. Then use the $150 figure that you determined it would take to cover your costs and make a profit.
give the customer a complete price of the time @$150/billable hr plus the material with whatever markup you want.
for example. customer wants you to extend a circuit and install a receptacle. You figure it will take you 3 hrs and material is $20.
let's double material, since it's not alot, and get our labor.
3*150=450
material = 40
quote the price of 490. you'll get it. You just need to explain that it's a fixed price. no guessing. no worrying on their part over how long it takes you, etc.
try this for 2 weeks, you will lose some jobs, but I bet you actually make more money overall.
worst case scenerio, in 2 weeks, you go back to losing money on every job but making it up in volume.
it's not easy. but final question:
if you could double your rate, but lose 40% of your customers, would you do it?