That Nagging Doubt

If you have a nagging doubt before you go on a date dont do it! Dont inflict a few hours of pain on yourself, not even if you're bored you will never get those hours back & you could've been doing something  much more interesting, such as washing your hair, doing the housework.
I've now learnt after far too many disappointing dates that even if theres an inkling of doubt it's not going to work.
One date ground me down to finally arrange that date after my initial "I'm pretty sure we dont have enough in common" feeling. Well it turns out we had even less in common! Then the dilemma is how long can I stay, how do I let him down gently.
So I have do to my usual buy them a drink back as they have usually bought the 1st & I feel I ought buy one back, but then that means I have to endure this painful date for longer. Why do I do that to myself? Manners I suppose or is it that I'm putting off the inevitable sorry but I dont think you're my cup of tea conversation, which I hasten to add I will always say at the end of a date not via text after but that's a whole other post in itself.
Maybe they are thinking the same but I'm pretty good at reading body language or I should be after all this time. Am I giving them false hope by buying another drink, do they think they are "in"!
I must stop doing it, believe in your gut feeling if its saying we have no chance dont take a chance, you could be missing the date you are meant to be on!