I don't know what "it" is. It could be that scarf that you walked by six times and didn't buy; it could be that plane ticket that will set you free; it could just be a cup of coffee when you just read in the news that coffee will kill you. The below quote identifies that you know what's best. YOU. You can hear that little sound in your stomach, or see the flashing sign that no one else can.
Here is this week's mantra:
“But who can say what's best? That's why you need to grab whatever chance you have of happiness where you find it, and not worry about other people too much. My experience tells me that we get no more than two or three such chances in a life time, and if we let them go, we regret it for the rest of our lives.” - Haruki Murakami (via Good Reads)
Although the author expresses in the quote that we only get a few chances in life, I disagree. I hope that as long as we keep choosing what's best, the opportunities will continue to present themselves.