Well as stated before the ketchup metaphor was not about blood. More about male stamina and giving a reference to that most guys don't last very long the first time and it usually comes almost out of the blue when the thing starts shooting.
Many get discouraged because of it and think something is wrong with themselves when it really isn't. Like everything concerning the human body, to be able to exert control over it you have to practice but practicing with your hand can only take you so far.
Best bet is probarbly to make sure you come first then focus all your energy on making your partner feel good and when you are ready again you are a bit calmer and in better control. (This can be done either during the act itself. Just make sure your partner aware that this is just a way for you to deal with the anxiety. Or before it if you can find some way.)
There is such a thing as going for seconds and thirds when it comes to sex (I have yet to meet a woman who didn't want to go at it a second and third time
).
The anxiety, expectations and misconceptions is the killer in this kind of very intimate human relations. I've found that getting off quickly then focusing my attention fully on her pleasure to be the best way to rid oneself of most of the anxiety.
And yes, I still feel it on the rare occasions I am with a new partner for the first time. The perk is that it will become easier to deal with as you gain some experience and familiarity.