This is not an original idea of mine and if I could be bothered I would point you to the true originator of this, that is to say if he didn't steal it from someone else, but none the less I heard this on the Tim Ferris Podcast to which I am a fairly new convert.
The idea behind this is to help with that difficult moment of indecision when trying to choose if you should accept an offer, an invitation, make a purchase or commitment. Simply put, just rate it a score out 10, the kicker being you can't give a seven.
The theory being that if its a 6 , well that's barely a C+, just above average, I'm not willing to give up my Saturday night for a C+. In truth I have regularly given up my Saturday nights for far less but that's not the point. No purchase that rates a 6 is going to take your hard earned dollars
The flip side of this is, if its an 8/10 well that's pretty good isn't it. If you got scored 8/10 for something most people would be pretty happy, stoked even. Who wouldn't want to go to that party 8, 9, 10 its an easy decision. An 8 out of 10 purchase is obviously something you need or really really want, buy it!