One day, you fell in love with this special person, whom in the
end, became your bf/gf over the course of several months courtship.
You feel that she is the one you probably going to last VERY long
(not speaking on the basis of marriage, but if possible and if fate
allows, it could happen). The both of you ride through the storms
of your relationship and enjoy the aftermath through a period of
probably 3 years. 
You felt that she/he may be the one....
You felt that probably no one else would take
his/her place...
You were utterly wrong.
You got to know this person (I called it the 'One') and you finally
discovered that ALL ALONG THIS LIFE, this is the person you
are looking for. You went beserk, despair or even resigned
to fate. Everything you desire and want in a lady/guy (physical +
characteristic) is found in him/her. He/she is everything you need
and ever hope for and probably if he/she becomes your partner - you
would be quite certain marriage will be an option in the future.

What will you do? You still have feelings for your gf, but VERY
strong attraction towards your 'One'. You felt that everyday you
are missing not your gf/bf but the 'One' and your craving for
him/her is getting more addictive every day of your life. 
Then, one fine day, you discovered that she shared the same liking
for you as well. 
You bleed inside from the turmoil and
torment.
***
What will you do? 