If you want a smooth ride on the cloud paradise you should leave your keys in the secret stash! Well, jokes aside, it seems we will be coming back and forth to our EC2 instances and, following good examples from @atgmello and @gabfr, I've come up with a simple step-by-step procedure to easy the journey whenever we want to rapidly connect to our instances.
After you set up your permissions with:
chmod 400 <your-pem-path>