What does "71" feel like? The comment suggests that there is some way that a "71 year old" ought to feel and that he does not feel that way. But, seriously, how does a "71 year old" feel? The answer is that there is no answer.
There is no "right feeling" for 71 or any other age. There is no "I feel 15" or "I feel 35" or any other age. There is only some mythical idea in your head about what you think might be true of someone else.
Have you ever heard someone say "I don't feel married." Who cares? You are either married or not married, but how you feel doesn't matter to that question. Men, reportedly, use this kind of a line all the time when committing or trying to commit adultery. They will tell the woman they have targeted that "I don't feel married" and she thinks this has some meaning beyond "I want to commit adultery."
We also do this negatively. We will say "boy, I really feel married today" when we are unhappy about something, or "I feel 71 today" when we are tired or depressed, but this is just as foolish.
The phrases have no real meaning. There is no "feeling married" and no "feeling 71," there is just you. Trying to compare your feelings to reality in this way is a vanity (to use Ecclesiastical language). It encourages you to think that there is something true that is not true, whether good or bad.
Try this. Quit this process of (1) looking at your feelings and (2) looking at your circumstances and (3) deciding how you think you ought to feel in your circumstances and (4) deciding whether you feel the way you think you ought to feel. Where does this get you?
I am 54 years old. That is a fact. I do not "feel 54" because I have no idea how 54 is supposed to feel. I am 54. I have a wife and four children and three grandchildren. I have a job and a class to teach and a blog to write and work to do. I have friends and family with whom to deal. I have Christ to preach and the gospel to witness about and bills to pay. I have to love my wife and love my neighbors and love my God.
There is no "feeling 54" issue for me. I do not have time to take away from loving others and living my life to try to think of such things.
Just live your life. Live today. That is all you can really do. That is all God wants you to do.