Ask HN: How to handle being sick?

I'm a freelancer, but I'm sure this applies equally to those traditionally employed. We all have deadlines.

How do you handle being sick?

I occasionally get the cold or the flu, it usually doesn't last more than a few days ... but those few days throw everything into chaos. A vacation or time off you can plan for ... but getting sick happens suddenly.

I realize I'm human and so is everyone else, but telling a client you were sick and that's the reason the project is a few days late ... it just doesn't sound right.

How do you handle it?