"Normal" pets you will generally outlive. Birds, on the other hand, are rather long-lived if properly taken care of. The larger ones will generally outlive their owners.

I have a pet cat named Willow, he's around 17 18 years old and it seems to be catching up with him, and it very much pains me to think one of the few constants in my all my memory is facing there mortality

Yeah, I understand. The first bird I got didn't survive very long - I only had him for like a month or two and then his bad habits or an illness or SOMETHING got him, and I was so heartbroken, even though I hadn't had him that long. :c

It might be a little bit easier if you see it coming. If you expect it. If it's sudden, there is no time to prepare.