Welcome to TE!

I hear you, and I'm here to say that commuting even on fairly busy roads is very doable. This is my (gosh!) fourth year commuting rain or shine, year round in Massachusetts, on a variety of roads. Here are some disorganized thoughts about commuting on busy roads.

1. I suggest scoping out your ride on a weekend some time -- actually ride the route at a time you know there won't be a ton of traffic (Sunday morning, for example). That gives you an idea of the road quality from a bicyclist's perspective. It's amazing how a road that seems fine in a car can be a nightmare on a bike: potholes, cracks, killer drains, lots of debris on the side of the road, no shoulders...the list of things to be aware of on a bike is nearly endless. Also this will give you an idea of how difficult your ride would be and give you a good idea of how long it would take when you do it for real.

2. Do the roads you'd ride on have shoulders? A very wide shoulder can make even a fast road perfectly rideable; just keep away from the car traffic (while, of course, avoiding the gutter and its associated debris) and you're all set.

3. Even if you don't have good shoulders, don't despair! The key to riding on any road is to remind yourself that you, too are a vehicle, and to behave accordingly. Put yourself where it's safest: Not as far right as humanly possible, but maybe somewhere closer to the right tire track. Also, when you pass intersections, think about pulling out even more, far enough to the left that drivers turning will see you and so that drivers coming up behind you don't crowd you.
3.a) Drivers may honk at you if they feel you're in their way. IGNORE THEM! Your safety is your first priority; drivers' convenience is way, way down the list.
3.b) You may have to ride assertively; it's scary, but drivers respect you more and give you more room than if you're cringing along on the edge of the road or (heaven forbid) on the sidewalk. In MA drivers don't automatically give cyclists space, so I have to claim my section of road. I do this by riding just to the left of the white line, unless there's a very wide shoulder; by pulling out into the right of the driving lane at stop lights and stop signs; by pulling out into the right of the driving lane in advance of potholes, intersections, and other known hazards; by riding predictably, and as much like a car as possible; and by signaling before making any turns or unpredictable moves.

4. See if you can find a commuting buddy. Some places have a system for setting up new commuters with experienced commuters who ride with you to help you build confidence. If that's not a possibility, see if anybody from your work or surrounding workplaces commutes by bike at the same time as you; team up for better safety and visibility.

5. Wear bright clothing and use blinky lights even in broad daylight. Any of the vests that are screaming yellow are great attention-getters and drivers give you wide berth when they see you in those. Also, I recommend the PlanetBike SuperFlash, one of the brightest fairly cheap blinky taillights I've ever found. I turn mine on no matter what the conditions; even a little blinking light will make you more visible, and every bit helps.

6. Is this absolutely the only way to go? If you can get on and off the busy roads even a bit, go for it. My route could be 11 miles, but I extended it to 13.25 miles to avoid very busy roads. A few extra miles are worth avoiding those semi trucks!

Sorry if this has been intimidating, long, and poorly organized. I'm sure I'll come up with more later. Good luck, and never give up -- never surrender!