Morning Petals...
There is some good advice on here, I'm certain your situation can be impacted from information gleaned here.
Now, this will be of interest to ya, I'm that guy!
For years the eternal pessimist. Still take pride in my ability to find at least 5 things about any given situation that are horrible, to everyone one you could come up with good.
Good news is I've been married 18 wonderful years and my wife sounds EXACTLY like you
. Early on we had some candid conversations concerning people we generally liked to be around. Funny thing, we both agreed negative people were a drag. (Generally, at the time, I didn't view myself in that category even though I squarely was.) My wife then would point out how people could view my rants as "negative" etc. Of course it wasn't a matter of one discussion, nor did she nag every day, but she was vigilant. Her final correction tool was this simple response..., "O.k., but what's good about it?"
That simple statement use to kill me. I'd be in the "heat" of battle, uncovering how this was second only to satin himself and suddenly all this rain would come rushing down on my parade. Bless her heart, my love still does that every now and then just for ol'e times sake.
I feel so much better now in every respect since I consciously choose to look at the positives. Ultimately he will need to "want the change", but helping him realize when he's being negative may speed that along.