The phrase "Let it happen" can often be used in a situation where someone may be trying to force something e.g. relationships, conversations, sexual encounters, sports, image, ect. This phrase is mainly used for advice for friends, but may not always be the right thing to do. The phrase is often used incorrectly in awkward situations, this is wrong. Usage of this phrase has to feel right, do not force usage as you would be contradicting as well as disgracing its meaning. This phrase accompanies a sort of ideology that some things are meant to happen, others are not, therefore one should not force things.
Guy: "Man I really want things to work out with Susie, but I'm not sure if I should force it or not"
Friend:"Dude, let it happen."
by Chilldude11 June 17, 2009
The end-all to any argument, dispute, declination of sexual proposition, etc. Popular among date rapists, but can be used whenever you have no response to a statement or question.
ex 1
guy: lets go to my room
girl: no, i should be going
guy: just let it happen...

ex 2
guy 1: hey i wrecked your car
guy 2: WHAT?
guy 1: dude just let it happen
by cchriss92 September 14, 2009