A cup of Tea to relax

Tea can not make you relax , it has caffeine in it !

Well, that's true for black and most green tea, but to me, tea is more then just it's substence and sometime a mug of something hot helps me calm down (and taking the time to make and drinking it while not working or doing anything else)

 a herbal infusion can help you relax. there are many type of plants and herbs you can try - lavender, chamomile, Melissa, Passion flower, berries, lemon grass, twig tea - there are a lot more.

I suggest you just try a few kinds and see what work best for you (and what taste good).

Most herbal teas are relaxing - chamomile particularly

Normal tea in theory wont relax you (because of the caffeine content) but of course the reality is that it often does. Probably by the fact that you break your busy routine to sit down away from work for a bit and drink it

Lilly is absolutely right.  I have found that a cup of chamomile tea near bedtime eases me through the transition from busy day to sleepy time.  It just sooths all those little jumpies out of my stomach and is a small slice of "me" time.  A touch of honey and a trace of lemon and it's off to bed for what has become a good nights sleep. 

 Just take care with the cream/milk.  I recently read an article that said a substance in cream/milk blocks the absorption of key healthful ingredients in tea (especially the green and black tea.)  I had been putting cream and milk in my tea to make it palitable.  However, after removing the white stuff, I found the chamomile actually had a much better taste without it.  

chamomile is very good, also Valerian root tea, which is where we get valium.