Stress
Grants aren't open-ended projects. They have firm deadlines—deadlines the grant writer holds final responsibility to meet. Unlike your empathetic English teacher who gave you a two-week extension on your essay on Ibsen's A Doll's House when your pet parakeet, Petey, died, grantmakers aren't going to budge on their deadlines.
Trying to write a proposal that depends on coordinating facts and figures from numerous people and places, all while under a time crunch, is a bit like herding cats. Sherri in development who's been silent on those statistics? Or Bill in finance, who's dragging his feet on the proposal's budget numbers? Good luck wrangling them. They may not feel that same pressure even if you're breathing down their necks.
If you're a freelance grant writer, you also have the added stress of finding enough work, so you can do important things like pay rent and eat. Hey, at least air is still free. You'll also have to deal with the joys of running your own business, like tracking expenses and remembering to send in your quarterly estimated taxes on time. Uncle Sam is a bit of a stickler when it comes to that last step.