Am I selfish.. what is fair

I am trying to decide when it is time to put Big Dog to sleep.. it is hard on him to lift him in and out of the car.. and that has to be done twice a day to get him to campus and to get him to the cabin.. and then sometimes a few times a day to lift up his rear end if he is stuck and he just cannot do it..
It gets to you.. when you want a dog that can jump in and out of the car to go with you.. that can really be a watch dog.. and that can get in and out of the house by itself..
Sometime it seems painful.. but most of the time..just an inconvenience and not to much fun to lift the smelly dog..
But then he likes to go fish in the water if people are down there.. and to be Paul's shadow.. unless dog cannot follow or get up and follow..
So is it fair to put him out of my misery, or is it selfish.. it is so hard.. I really think he has been a most tremendous dog.. except for nights when he wants to bark too much..
I have really liked him a lot.. I cried a lot last summer when we almost put him down.. now here it is almost another year.. and he is getting slowly worse again.. especially trying to go back and forth to the campus..
He does not like being alone.. he wants to be with his people.. his pack...
sigh..
to put him down I need to schedule a few days ahead.. that is hard too.. kinda chicken to do that.. have talked with the vets several times about it.. so now know the ins and outs of that step..
I gave him another pain pill tonight. I think the in and out today has been really hard on him.. he does much better when not forced into the car.. I think it has something to do with his back bone as well as his back legs.. sigh..
so.. Am I selfish if I am ready to put him to sleep.. or is it fair or unfair.. and I don't know..
sigh...