To Sequel or Not to Sequel

I've been thinking about which book I want to tackle next. I've got a whole gaggle of options, from vague ideas to outlined concepts. They are all clamoring for attention, of course. But I can't do them all at once, so I have to make a choice. And as I mull, I realize that a big part of the decision will be if I want to write a sequel to an existing book next or a completely independent book. Which brings me to the issue of sequels. Since I write novellas, I don't usually leave myself a ton o...