One space or two?

I sometimes find myself angsting about minutiae.  Today, it is the humble space bar.  How many times do I strike it between sentences?

I’m not old enough to have ever used a typewriter, except for that period in high school when I convinced my mom that a typewriter would help get my creative writing juices flowing better than the computer.  She lovingly found a beautiful electric typewriter for me at a garage sale, cleaned it, and presented it to me.  Initially, I was ecstatic.  Now I could be a real writer!

Then the realities of actually working with a typewriter set in.  I hadn’t realized before how much computers actually did for me.  Simple things like line spacing became a nightmare.  I am thankful for my electronic helpers these days.

Still, when and why did I begin putting two spaces between sentences?  It is a deeply ingrained habit, one that I didn’t think much of until recently when I started seeing some posts from friends on facebook about the issue.  I began to worry.  Does my double-space make me less cool?  I became convinced that people were reading my work and mocking the spacing.  I could practically hear the whispers and giggles!

I tried to break the habit, but that only made things worse.  Some sentences got a single space while others received the double space.  What to do, what to do?  Would anyone take my writing seriously with the grotesque double-space leering up at them?

In the end, I am still unsure of how to approach the ends of my sentences.  Habit and muscle memory dictates the double space.  Yet correct grammar informs me that a single space is the only correct ending to a sentence.  Perhaps the most important thing is consistency.  Double or single, I should probably pick one and roll with it.

So how about you?  Do you double- or single-space?