What a Cancer needs more than anything...If you're going to date a Cancer native, you need to come with your A-game, because they bring theirs!
This sign needs to know they can trust the people they're letting in, so they need to know all about potential friends and partners, particularly at the beginning. For you, your heart is just too fragile to take any chances.
To be fair, Cancers go out of their way to show others loyalty as well. If you're in a tight spot, having a protective Cancer on your side isn't a bad thing. They want to demonstrate their support to others, as well as the power of nurturing and love.