I have a 20 month old male german shepherd who is quite nice natured and wants to play all the time in the house but the second I take him out he becomes a nightmare pulling on his leash, trying to chase cars, people, dogs etc etc and I am finding it harder and harder to control him and am getting more and more tense about it every time I take him out. What can I do?? I have been told I should try to socialise him more but no-one will come anywhere near us when he behaves like this. I am sure he just wants to play. Please help. He wont listen to a word I say