How do you feel when you've been left on 'read' for a long time and what do you normally do about it?

For me it depends on the situation, I will normally wait a few more days and try to catch them up if they haven't responded. 🤷‍♀️

It isn't a nice feeling but I understand sometimes things happen, I get a tad worried if I know the person has been available to chat and it was an important message though...