i find singing along to music, having the window down, have a bottle of water there to sip. also there is the number plate game you can play by making up names on the number plate infront of you silly ones, rude ones whatever you like or make up names or add up the numbers, this particually helps when you are stuck in traffic. deep breathing will help, i used to be the same pulling over about 3-4 times on about a 30minute journey. i have got better by relaxing, but still find it difficult in traffic but do not avoid it as it makes it worse as you will never go in traffic again! I LEARNT THAT THE HARD WAY