The solution is to install the PersistIQ extension; this will block PersistIQ from counting when you open an email. If you don't use Google Chrome, follow this guide.
Why do you need the chrome extension?
The way Gmail, Outlook and most modern email clients are designed, we are unable to identify "who" really opened the email when someone opens an email. It's a feature built by modern email clients to protect the privacy of their users. This means every time an email is opened, no matter who opens it, we identify that open as being from the prospect.
The chrome extension block the PersistIQ tracking code so that opens don't register for you!