To "Old and Now Slow". Are you varying your runs? Taking a day off after a harder one, or cross-training on the bike? How is your weight now, and do you know your body fat? Do you have any residual issues from cancer (chemo can result in congestive heart failure, so weakening your heart muscle and so limiting what's possible, plus can mean you are better off staying at a more moderate pace)? What is your weekly mileage right now, and do you try to vary hard/easy weeks right now.
I agree with others that putting the ego aside is important, but also stepping back and assessing yourself like a coach would, so can you talk with someone local who can assist, observe and suggest?
I do like that you are doing some strides, just picking up the pace a bit helps make the runs more fun. Are you using a heart rate monitor at all? Checking morning pulse to make certain you aren't overtraining for right now?
I agree, too, maybe just a plan to do an event for others, like a cancer awareness event, for example, in which your family joins you?
Random/run-on thoughts here, for what it's worth.