Everybody waits to respond to some messages. Everybody knows this. Just because someone knows you've read their message doesn't mean you need to respond immediately.

Read receipts make messages more useful. You don't have to guess if someone is a frequent email-checker. You simply know if they've seen it or if they haven't. If they haven't and the message is urgent, you can try other means of reaching the person.

Relax. It's going to be okay.