He doesn't know when it happened. He doesn't know just when his best friend in all the galaxy became more; when the man became indispensable to his very soul. And anyway, even if he knew, it wouldn't change what's happened to him. It wouldn't take away the fact that his heart was given away without his knowledge - almost without his consent.
And now, he can hardly bear to be near the other, or to be away from him. He wishes and watches, and he waits; but he does not hope, because there is no hope. The most he's going to be able to get is to be at the other's side when he is needed.
He realizes with a jolt of fear that it would break him utterly if his friend were to turn away from him. That would be the final straw - the last of a weary load in a life that has been full of burdens. And he knows that he cannot do anything to jeopardize his friendship, even if it means breaking his own heart.
It occurs to him - not for the first time - how poisonous love is. It is a poison; a sweet, intoxicating poison.
And that, he realizes in a flash of bleak truth, is what makes it so very dangerous.