Some beginner riders constantly watch the road behind them, or fixate on their rearview mirrors, as if expecting Interpol to be chasing them. This comes at the expense of watching what's ahead, and usually stems from the falsehood that General Motors owns the highway and a mere bicycle can only trespass upon it if it dives onto the shoulder whenever an overtaking car approaches. A better idea: buy a LED blinker, and don't sweat it.
An important step to achieving any goal is to make a mental commitment to it. But the first step is to set a realistic goal. You don't have to give up your car cold turkey. Maybe start by promising to ride your bike to work one day a week. Later increase that to two or three days a week. That gives you some flexibility to adjust your biking schedule based on the weather and how you feel.