Sounds like right person, wrong time (for him). The right feelings can hit at inopportune moments and these unfortunately oftimes make you have to choose one person over the other and in this case you got the short end of the wedge. I really do not beleive that it is your fault here and you should never think that. Nor should you think that it is something that will only happen once or that you will never feel it again. One day you will find another person who awakens the same feelings or who awakens different feelings that are so good you won't care any more that they are different and this time it will be the right time for both of you. The important thing is that you are open to this and ready for it when it happens. Each relationship we experience is a stepping stone, an education towards that perfect one which lasts forever and if each one you experience turns out not to be that one then that is fine, just move on to the next having learnt something new.