As it sounds, there are a few circuit breakers throughout the body that when pressed with enough force they manually prevent ejaculation. Learning to use them properly takes a little time, but once you are familiar, these can provide the ultimate emergency safeguard against any ejaculation before you are ready.
MILLION DOLLAR SPOT
A long time ago a Tantric Master named Lu the Immortal discovered a place on the body that when pressed with adequate force would manually delay ejaculation for as long as required. He ordered his disciples to guard this secret closely, and made them vow never to reveal it to any outsiders. The legend goes that around the turn of the twentieth century a wildly wealthy American, (who will go un-named) was on a journey in Western china, home of the disciples of the legendary Lu the Immortal. He had heard of their abilities, and sought to learn the ancient ways in order to improve a modern problem of his own.
Most of the masters he encountered were taken aback by his loud and abrasive mannerisms, and if they told him anything, they spoke only in intentionally vague and mystical language. In one of these sessions in particular, a younger master (and by younger I mean in his early 60's) was repeating through a translator the fable of the cobra. "While coiled, the cobra is quiet and poised. But when he strikes he becomes vulnerable." The American had simply had enough. In a wild outburst he exclaimed, "God, Damnit, isn't there just some spot I can push!" A very old and wise master who had been sitting in the corner of the room broke into a very uncharacteristic smile. This caught the American's attention.