http versus https links

So I have an SSL certificate for my WordPress site and both http and https work fine. My question is how do I code links in posts, etc., so that when someone clicks on a link within my site (an internal link), if they are using https the link will go to https://page, or if they are using http, the link will go to https://page. When you code a link, you put one or the other and I want it to follow whatever the person is using. Not really a WP question as this would apply to any link on any site, but I am curious. Many thanks in advance,

Drew