Using the brakes hard on new pads will ruin them! Depending on which speed you've braked from the last 10mph will be a bit dodge on new pads as they won't have bedded in and therefore will be more prone to fade.
As vwsystems says, take it easy for a while (50-100miles should do it).
Also, find a clear bit of road and dab the brakes with your left foot at about 30mph. Not enough to drastically slow the car but just until they start to bite, this should help bed them in...