FWIW, as a Polish twenty-something, I rather expected Russia to mellow out as it becomes more democratic over time. As of approximately the time of the Crimean invasion, that opinion has shifted a great deal.
Overall, I'm happy that Poland is a NATO member. At least it adds another deterrent (or failing that, a speed bump) in the way of a Russian invasion. Were NATO not to exist, and Russia to re-awaken it's conqueror instincts at some point, we'd be screwed yet again.