It depends on the situation, but I do not like to jam on my brakes if I'm too close so in those situations I will just go through.

Where I live, main highways have warning lights ahead of the traffic lights that will start to blink if the light will be yellow by the time you get to it at the posted speed. So when I see those go on I start to slow down even though I still see a green light because I know from experience that it will be yellow or red by the time I get to it.