As mentioned, every women is different, however for me it has to do with a guy being too aggressive when he starts out. For me, it's gentle and soft, work your way up to more pressure and intensity over time. And about time, take it slow. It's not a sprint to the finish. I hate when a guy goes right for my clit and starts licking hard because not only is it uncomfortable, like being tickled, but it absolutely kills my chances later on to have a orgasm. The sensitivity is all fucked up and I don't want him to go anywhere near my pussy once he's done that. I'll pull away in a second and kick a guy hard who does it. It's like, 'what the fuck dude, this isn't a pie eating contest!' (well, you know). And I tell you what, if he screws up my chances he can forget about his. Game over man, put willy away.