Experiences with cockatiels who are left alone after their mate died.

Hello reader. Last week one of my tiels died after being sick for a little while. Im now left with one lil guy and im just so worried about him. Im doing everything I can to make sure he's comfortable and he seems mostly happy for now. throughout the day he's whistling and going around his cage and my room seemingly happy. At other times he's very stressed and uneasy tho and Im not sure what to make of it. I get that he probably needs time to adjust so Im trying to spend as much time with him as possible. I was wondering if anyone here has similar experiences with losing 1 bird and being left with the other and how that ended up going. Im worried he might get sad since im not always around, or even worse get sick like my last bird did.

I understand that this question may have been asked a milion times on this subreddit but right now I would love to hear from some people and get into conversations, since I dont really know anyone with birds or people to ask questions about this sort of stuff.