Become an experienced bullshitter. No, I'm not kidding.
If you can't look at your notes and make something in an instant, you need to learn how. No matter how much you prepare and put loose plotlines and hooks together, your players will undoubtedly find a way to throw you off your game...
You two seem to get it. I'm pretty new to the whole roleplaying thing, but I've been writing solo for about 15 years. And the fact that someone should feel that they HAVE to participate in a hobby is... baffling.
I dunno if this is unpopular, but you should literally never feel as though you HAVE to reply. It's words to a story. If you don't get a post up for a while, it's okay. You should be considerate and tell people-but you never have to reply if you feel you can't or even just don't want to.