How do I prevent my veins from bulging when I am angry or stressed?
It is not possible to prevent your veins from bulging, because this is a natural physiological reaction. What you could do is to learn to control your anger and also avoid stress so that the veins don't show up at all.
HULK... SMAAAAASH! dunno how that helps but I had to say it. try not getting angry or stressed [like bruce banner does!]
Drink a glass of water........
Sounds like you could try to manage your response to stress, like practicing breathing exercises. Best wishes.