How Do You Tell Someone You Miss Them?

How do you tell some one you miss them, some people say its simple as 123. But its not. You want to tell them you miss them and need them but, every time you get close to telling them you lose your train of thought. You even write a letter but you can't persuade yourself to give it to that person. You spend your day thinking about them and hurting because you just can't find a way to tell them. Your scared to tell them you miss them because its weird and awkward. But at the end of the day, the one you miss the most walks up to you and says " I missed you!"