One of the most important things in a relationship is that you have to emphasize your feelings to your partner. You should do it as frequently as you can, the best would be to tell her every day.
Not only on special days, like Valentine’s Day, anniversary or birthday, but every single day. In your life there are lots of problems. You have barriers at work or at home with the family, neighbors, traffic, etc. These problems cause stress in your everyday life. That’s why it is important to know that somebody loves you, that feeling helps you to solve these problems, because it makes you stronger and gives you inner power. Do it every day!