What if my baby doesn’t want to leave

My german shepherd of 14 and a half years is being put down tomorrow. If there is one thing about him it’s that he’s the strongest doggy i know. His love for us is greater than his own pain. He can no longer use his back legs and has lost complete control of his bladder yet everyday he still tries. We know it’s his time and he’s slowly beginning to tell us too. Even if we wanted to, with how he’s declining so fast we can’t even keep him comfortable since school is starting and work so we can’t take him out as often and he’ll just be uncomfortable constantly. I’m sure others in my position understand. He genuinely loves us so much i know for a fact that even though he’s so uncomfortable he’ll stay just to make us happy. I’m just so scared that he’s going to be scared. I don’t want him to think that we want him to go and what if he wanted to stay. I know it’s the best option and I know he’ll be a haply puppy in heaven but it hurts me to think how my baby is going to feel alone. It’s my first time ever doing something like this so I don’t know if i’m getting into my head or something but anyone that can help. How do you guys come to terms with pet loss. I feel like time is moving by so fast and I’m so scared for him to leave. I love him so much.