What happens if you can't travel because of your health? Will agents and publishers not want you or your book?
With the advent of Cyberia and radio interviews by phone, you can do a LOT to promote your book without ever leaving your lair.
Donna Leon lives in Italy and thus unavailable for US travel very often and her books do quite nicely.
Lots of other authors don't tour in support of their books for one reason or another.
You can cross this off your things to fret about!