Simply replace the unfilled areas such as "" and "[date]" with your information.
I simply do not have the nerve to tell you this in person. So, I am writing to you because it is the only way I can say everything I need to say without making a complete fool of myself.
The best way to begin is to say that I have the biggest crush on you. It is more than a crush; I am completely drawn to you in every way. I get such a rush of emotions when you [some interaction between writer and receiver]. I love the way you [verb] and the way you [another verb].
I know that I should've said something a long time ago, or perhaps not at all. I just couldn't go on any longer pretending that you don't mean the world to me. I want you to be that special person in my life. I want to hold you. I want to fall in love with you.
After you read this there is a chance that things may never be the same between us. I had to take that chance. If you could ever love me I would spend a lifetime proving myself worthy.
Know that you will always have my heart.