First, the fear. Sounds like you have gotten slapped in the face with the suddenly inescapable truth, that you REALLY ARE GOING TO GET OLDER AND ......
That is not making light of you feelings at all. When something finally happens that forces one to see that they really are mortal, it messes with the head case. We are programed, probable by genetics, to believe we are more or less indestructible in any normal activity during our teens and twenties. But after that, certain body functions (i.e. healing) slows, and our programing seems to change to more cautious as well. Then eventually "SLAP!", some life event happens, and it comes crashing down on us psychologically. This seems to me to be where you are now.
Everyone has to cope with it in their own way. I suggest short daily rides, with your wife, since you previously enjoyed riding with her. The spending of time with her will help kick in other psychology that will help counter balance the fear. After all, riding with her previously was a bonding experience for both of you. Be sure to tell her what you are doing, and why you "need" her to be there with you. This helps bring in more bonding, and more positive psychology that is associated with her. Then get on the bikes and ride. Increase your distances by say 10-20% each week, and I would bet you get over it in short order. I once read it takes three weeks to establish a new automatic behavior (habit), and three weeks to stop one. Assuming that is correct, then you will probable be more or less your old self by the end of a month.
Lastly, we are not talking about logic, so that is not the best course with dealing with a fear. It is much more effective to use emotions to deal with emotions. This is simply the way people are put together.
BTW, I grew up wrecking and riding etc, so not allot bothers me. However, my female counter-part got a real headjob done on her by her dad and his fear of his own shadow. She has been riding with me, and the fears constantly resurface. I remind her of previous fears she has already gotten past, and how she would tell me "I can't", only to find out "she can" after all, but don't press her. Just plant the seed and let it grow, then normally a couple of rides later, she gets pasted that as well. Whenever she reaches a new goal, be it distance, or a significant fear, I make sure that we do something fun, or a treat (ice cream cone is a fav), so that helps bring in those basal reward systems, to make further fears less effect. And yes, it has been working well. And yes, I have made sure that she knows exactly what I am doing, and why.
Keep it up, keep working, and you will have the reward of knowing that you won over a fear, and that many many people are never able to get past these types of fears, but YOU DID!
QT