How come almost inevitably when I develop a close friendship with another woman I develop some type of awful crush on her?  How do I stop this from happening?  I just want to be able to have platonic relationships with women and I suck at it.

I am not comfortable with this happening.  I am monogamous.  The idea of being sexual with someone other than my partner (who I do love very much) upsets me.

But ALSO WHY DOES THIS KEEP HAPPENING?