Love is difficult to think about because there are so many different types of love. The love you have for a parent, a friend, a sibling, a significant other are all similar but also very different.
Another reason is that it's one of those things that needs to be felt rather than imagined. You can think about what it's like to be in love all day long, but once you're in that position, your whole look changes. When you're not in a spot of love, it's hard to truly grasp what it was like back when you were in that place. It's similar to fear. You can try to remember a time you were really scared, but the true essence of how you felt then can only really be experienced by being at that level of fear again.