Sincere love requires concentration and effort. It's not just a feeling. It if is "easy to love" someone - you may be missing the mark! Sincere love means that you sacrifice to help others become better people, to help them overcome the challenges that keep them from living as God created them to live. This demands all our time, our convenience, our money - and definitely our personal involvement. (Writing a check is not sincere love.)
So when you find yourself thinking that you love someone, ask yourself how you are enhancing their life and what that is costing you. That is where you'll find the measure of your true love for them.