Popup showing too much – every page – can I reduce?

I created a great email opt-in popup for my mailchimp newsletter that I love. However, it is showing up too much. If the user goes to my homepage it shows up and if they X out and click on any of my blog posts it comes up again. Can I reduce the popup to showing up only once per session? I don’t want to limit it to just showing up on my homepage because some users are drawn to specific posts on my site (for example if they click on an article from a pinterest pin) and I want them to see it too. I just don’t want it to be annoying and come up every single page they go to. Thanks!