I do customer support for a non-technical market. Name an issue, my customers have had it -- they can't print when the printer isn't plugged in but the print later button doesn't work, etc. (You might describe this as "I can't save.", since your model of what a program does is a bit more sophisticated than hers is. Plumbing that mental model took a day of wading through some fairly exasperated emails.)

A lot of small software developers think that I must be going totally insane with questions like that. Honestly, no, I could do this forever. I have two main secrets.

One is relentless focus on ease of use, because you CAN find ways to take your existing program, business, and business processes and simplify them so that there are less places to have errors.

The other is that you can never have contempt of your users. Not even quietly to yourself. Don't call them Help Vampires, even mentally. You'll poison yourself, you will start to dread the You've Got Mail light, and you will find answering questions exhausting instead of a routine task which you're paid hundreds of dollars an hour to do.

P.S. Charge more. If there were such a thing as Help Vampires, and there is not despite the fang-marks in your neck, charging more would be a cross against them. You'll almost invariably find the most difficult people at the bottom of a market.