As human beings we have a survival mode, and part of that mode is often hiding how we feel. When someone hurts us, or to have the upper hand. Sometimes we try to take emotions out of our relationships thinking that's how you make the clear decisions. It's not. Marriage and relationships are all heart. Sometimes they don't make sense. Sometimes how we feel doesn't have any bigger reason than that's how we feel.
I'm not saying you have to constantly be crying tears of joy over how much you love that person. Being forthcoming with your emotions can be as simple as saying I love you every morning, smiling at them out of the blue, or just holding their hand while you watch the nightly news. Every one has a different way they show their feelings, if you pay attention to your spouse you'll know what they need from you.
Don't waste time, make sure your significant other knows exactly how you feel about them. Be emotional. No one wants to be in a marriage or relationship where they have to question if the other person is still in love with them.