need some answers from someone near my age and previous interests.

I am 64 have always been very active. I jogged,worked out at a gym,taught tennis,played tennis and many other things for physical exercise. am not over weight watched my diet,mainly vegetables yet i still had to have a triple bypass. I have many questions like how long before your stamania returns. Will the heat and cold tolerance get better or will that be something you will always put up with?? when you overdo is it normal to get an upset stomach?? I am seeing other things now that i didnt have before and am really wondering how much of this is permanent and how much is temp. It has been ten months now and my DRS. say i am doing great. Well none of them have had this so even as smart as they may be none of them have had this and probably not as active as i was. I would love to speak with someone who has gone through this and have remained active. THANK YOU THE HOBO