Do you run trading journal???

Do you run it?Is it helpful to you?Is it really necessary to have one?
Thanx in advance for respond!
VTK

I have a file that I keep a record of every trade I have ever made. I print out a screen shot of entry and exit and put down my thoughts. It is very helpfull because when I am not trading so well I can look back at when I was trading well and get back into the better mindset. I think is a must for sucessfull trading, otherwise you are just stabbing in the dark and acting in a random way.