Remus found love a scary concept, not in the way that most people do, he was never afraid of getting hurt, he was never afraid of commitment, he was never afraid of rejection, Remus was afraid of doing nothing but hurting those around him.
This was because growing up, Remus had only ever associated love with pain, from a very young age he recognised the look of hurt on his parents faces when they looked at him, when his father insulted the fearful werewolf Fenrir Greyback, Greyback attacked Remus, the thing his father loved the most, from then on in, the more he loved people the more they seemed to get hurt, the more pain stricken their faces became when they looked at him, the more guilt he felt.
When Remus found out he was going to Hogwarts he realised that he would probably need to make friends, but this was something he didn't really have much experience with, he never really got the chance to make friends as he was stolen from his childhood before it really had the chance to begin, he hoped that friendship would be the safe kind of love, the love in which he was the only one to suffer, as he believed was right.
Friendship worked out for a while, everyone was safe, Remus disappeared once a month but no one was hurt but him, this love was working just fine. Then his friends got curious, but they stayed safe, Remus made sure of this, this love was surely more intimate than before, but it was still working.
It was all working, it was working well, until something new happened, until Remus suddenly got this weird feeling whenever he looked at a particular friend, until the laughter of a particular friend made every day a whole universe better, until he fell in love with a particular friend, until Sirius Black turned his world upside down.
Now extra precautions had to be taken, Remus had to protect Sirius with every inch of his being, he didn't want anything less than to see Sirius hurt, to see Sirius' face become more pain stricken when he looked at him, to feel any more guilt.
Little did Remus know that Sirius felt the exact same way, Sirius felt the same guilt, the same hurt, the same fears.
Remus found love a scary concept, in the same way that Sirius did, they were never afraid of getting hurt, they were never afraid of commitment, they were never afraid of rejection.
Remus was afraid of doing nothing but hurting those around him.
Sirius was afraid of doing nothing but hurting those around him.
so they never hurt each other.