I had the opportunity to see first, to be reminded of it rather, how bad and good rolls can knock you all around at the table.
In running a game for a bunch of youngins this past week I watched one of the roll horribly all night. He kept getting more and more downcast, angry, frustrated. And then when his missing streak ended and he hit he rolled a "1" for damage. He hit next time and rolled a "1" again and then a "2". I thought the poor guy's head was going to explode.
It was compounded by another players bad luck turned awesome with a natural 20 on his death swing (I often give a falling character a final swing, whether its extra or not) scoring an instant kill on the crit tables. This drove his frustration to unbelievable heights.
So after that he was alone against 1 orc with 7 hit points. Another 10 orcs were charging, but their morale was very low (as 20 of their people were already dead). Well dude man rolls, wins initiative and then swings. Everyone is watching. Boom! Its a hit. Then the damage. On top of all the 1's and 2's and the misses he was all bound up and keyed to a fevered pitch. When that 8 hit on the d8 he went absolutely insane!
Arms in the air! Out of the chair! Shouts and screams that devolved into simple growls and grunts of pure adrenaline and power!
It was pretty cool.