Gary, what idiot told you you only have 4-5 years left. It just ain't so. Nobody knows and no responsible oncologist would put a number on it. Having said that, I was told ten years ago to live every day as if it might be the last and hope for five years. Wrong! With pretty high PSA number and Gleason score, I'm still battling on, enjoying life and I think you should, too.
There are lots more treatment options available now than ten years ago and I guess that you will shortly learn of them. My advice? Don't panic, stay positive and yes, enjoy, every day of the rest of your life. A positive outlook prolongs life, I believe!