Seriously? Never? Try to have a meaningful relationship without ever making any assumptions. Heck, you probably couldn't even get out of bed in the morning, much less make it out of the house, if you never assumed anything.  Sure, you probably shouldn't assume that the sweet young barista wants to have sex with you simply because she smiled when she took your order, but it would be fairly safe to assume that you will get the skinny latte that you ordered, unless she needs for you to wait here while she gets change for your fifty back down the alley. Then it will probably be safe to assume you're an idiot.  But if you need absolutes to guide your life, then here's one: Never live by absolutes.