Difficulty in Guitar Lessons

I have playing guitar for a while now, but never took formal guiatr lessons till recently. And I was pretty comfortable playing in my own style.
Now, I thought of attending some guitar lessons and my instructor asks me to hold my pick in some different way. Now, the problem is I can't play the songs that I used to play with my original style.
So, what do you people think I should do? Follow my teacher's suggestion and relearn everything I learnt before or Should I retain my old picking style?
Moreover, my instructor is adamant that I change my style....

@ 6String,
It would be nice to know WHY your instructor wants you to change the way you hold your pick. Ask. It could be that the way you are currently holding the pick will keep you from progressing to more complex songs. So, you should ask why and if the answer makes sense you should change your style. After all, you are paying this instructor for his/her knowledge and help. You have a camera, could you take a clear picture of the way you hold the pick now and one of the way your instructor wants you to hold it so that we can see?
Phip

Evil... well Ive been played guitar by my own for years... I learned to play with my own style for my kind of stuff, but it limit me to play variety of music.

If your teacher is good (this is what Jazzy always been spoken), If your teacher know what he is doin, re-learn your stuff if possible... for me its not possible anymore, but I can live with that. But since if you are played like under year or two, I strongly suggest you to change your style away from wrong or bad one.

Like always when people start to learn stuff bythemselves without teacher who already know stuff, it is very possible that you learn something in a "wrong way".

It's very likely you have bad technique and should change, but definitely ask him why when he asks you to do things you're not sure of.

Can you take a picture of a close up of the way you hold your pick?

If he says what you're playing sounds bad, then I'd change it, if he doesn't I'd keep to it for those songs only, then start learning new songs the way he's asked you to hold them, once you get used to it, you should be able to play your other songs you knew the same way.

Sorry to reply so late... the work is killing me...
I think I'll do what my teacher says. I found I couldn't play faster riffs with my older style. My older style was good for playing leads which I used to do for the most part.