The grey squirrel is a very common animal in Eastern Canada, especially in cities where there are lots of trees and food. Not threatened by urbanization, it greatly benefits from the presence of humans. You'll need to be patient because controlling squirrels can be difficult. If you feel you're going nuts, perhaps you should give meditation a try!
Although grey squirrels have a preference for tomatoes, they feed on the fruits and buds of several other edible plants, and it seems to enjoy digging out the rhizomes and bulbs of certain plants like tulips. Often, they only make a few littles holes in cucumbers and tomatoes to suck out the juice they contain.
A few solutions exist to keep squirrels away from the garden. One of them is to use a commercial repellent like the Wilson Predator Animal Barrier. As its taste and smell are highly unpleasant, just spray the plants you want to protect to keep squirrels at bay. For optimal results, you'll need to spray several times a week, especially after a rain event. Do not spray directly onto the fruits and vegetables you're growing as it could change their taste.
Another option is to cover your vegetable plants with agrotextile or wire mesh from the beginning of the season, and this, up until it's time to harvest. Obviously, you'll need a structure or hoops to do that.
The third and last solution consists in installing a motion-activated sprinkler in your garden. Simply attach your hose to the sprinkler and place it near the plants you want to protect. Whether by day or by night, it will activate as soon as an animal gets close, which should deter it from coming back.