When You Realize You Love Someone Who Will Never Feel the Same; that "Oh Fuck, I love her" Moment

  What do you do is this situation?  The moment that you discover you love someone, yet they will never feel the same.  You may be friends, or just co workers; although you may not be really close to them, you know enough about them to love them.  They become the focus of your world, just talking to them about their day makes you happy beyond your comprehension.  You want to learn about them, you want to know all their pains in life.  The sound of their voice makes you smile; they pop into your thoughts throughout the day.
  Yet, as strongly as you may feel about them, you know they will never return those feelings in the same way.  Whether they just outright tell you that or do it subtly, you just know.  The great majority of the time, it's a subtle message you get; they text other friends all the time but ignore you, are unwilling or reluctant to tell you much about themselves besides the basics, maybe make plans to get together and then cancel at the last minute.
  Whatever the case may be, they are putting up walls between you and them, walls that only they can bring down.  You find yourself having that "oh f*ck, I love them" moment; the one where you know that it's only going to cause you pain in the end to love someone who doesn't love you; nevertheless even though you know that, you can't give them up in your heart.  They may "like" you; indeed, most certainly they do if you guys are friends.  Nevertheless, they will hide many things in their life from you, and when they are upset, excited, or just feeling the need to talk to someone, they would rather not choose you as that person.  Of course, if you talk to them about the friendship, they may say that they value you and consider you a very close friend, yet those two words that have become so critical in a relationship are missing; "Love" and "Trust".   For if one of you feels that way while the other doesn't, you can sometimes wind up finding yourself, as I like to call it, "royally f**k*d"
  The reason for this is when you get to this point, unlike some other situations, you really are between a rock and a hard place; you can either accept that they will always hide things from you and never return your feelings, or you can take the "unthinkable" route and part ways with them in your life.  I call it "unthinkable" because when you love someone, as people know, the hardest thing for you to do is give them up or lose them.  Yet what can happen if you don't move on without them, is that everyday you may wind up either pitying yourself for not having the will to move on, or just taking a bitter attitude towards the entire situation and being miserable all the time.
  The choice is one that can be discussed with the one you love, yet only to a point.  For ultimately, when they have already said that they will never fully let you into their lives like you need, the time comes when you need to decide which is best for you; what you can live with.  Sometimes it feels like you can live with neither, yet you still need to make it; the effects of that one decision can follow you for the rest of your life.  I think you need to let them go, or accept it without being hurt. For in the end, everything being equal, loving someone and wishing that they will love you back, yet knowing they won't; that's no way to live.