It's Yer Choice
Dogs are opportunists meaning that they will take what they can get when they can get it. Ever since your dog was a young puppy they have learnt right from the start that if they want something they have to rush in to get it. In a litter of let's say 8 other puppies if your dog hung back and politely waited, it wouldn't survive. The issue being that by the time your dog joins your family as a puppy, life has already taught them that to have a resource that they want, they must be fast and strong in getting it.
It is important to remember that lack of impulse control and the behaviours that define it are normal behaviours for your dog, it is us who don't like it. Taking what one can getrmal not is a species, specific behaviours. If you dog jumps on the counter they aren't being naughty, if your dog woofs down your steaks that you dropped, again they aren't being naughty. They are just doing what they have been brought up to do. They haven't been taught appropriate manners to compliment living in a very human world.
Really in lack of impulse control is a normal species, specific behaviour for a dog.
When our dogs are born and grow up with their litter-mates they learn right from the start that if they want to have something in life, they should rush in and get it.
No puppy ever gets anything by politely sitting back and letting his siblings go first!
So by the time they come to our house life has already taught them that if they want to have a resource, they should be fast and strong in getting it. If they are not, their desired object just disappears! (because someone else gets it)
Now we want to turn this concept around and teach them that from now on, if they wait they can have things but if they are impatient these things may disappear.