I have the same problem and been playing for ten years.

Listen to your teacher, I never had one and now suffer for past mistakes.

The worst thing with that problem is your thinking about shredding more than playing. I know I am. I feel frustrated about my left hand not being fast enough but you need to control those urges to shred.

Also, in my case, in tend to push too hard on my left hand. Wanting to play as fast as my right hand I sometimes feel burns in the left hand. We all know what that means, tendons and ligaments under tension! Wath out for this. Buy starting slow like the other suggest, you will also train your tendons and avoid painfull injuries.