Most people want to help others because it brings them joy.
Over time, this "reward" for helping others (usually in the forms of dopamine or serotonin to the brain) has crept into the arena of avoiding hurting people because it makes us feel bad.
We've developed a bias towards good news and found a way to put a positive spin on everything, so we can avoid pain. But digging a hole in the sand and sticking our heads in it has led to an epidemic of over-promising and under-delivering, labeling what we hope to be true as 'fact', and using the word "should" way too often (i.e. - that's how it should work).
We do this every day of our lives:
I'll call you tomorrow.
Pick you up at 8:00.
Expect an offer by the end of the day.
In sales, it's hard to avoid this kind of positive language, because if you don't make these promises (regardless of whether you intend to fulfill them), someone else will make those promises, and they'll get the sale. However, even as skeptical we are with salespeople these days, we still fall for it time after time. Why? Because the salespeople aren't the only ones lying to us...
No matter how many times we've been burnt in the past, we have this stubborn hope that this time will be different. We want to believe it.
We lie to ourselves for the same reason we lie to everyone else: We don't want to let them down, and we definitely don't want to let ourselves down. Where does this lead us?
Short term pleasure, followed by uncomfortable and impossible situations.
If you have to lie, or sugarcoat the truth, or over-promise when you know you will under-deliver... you are already in an impossible situation, and your chances of victory are slim to none.
Speaking of... does anyone know the difference between a 'slim chance' and a 'fat chance'?