I find it easy to find small moments of hapiness throughout the day. Just walking to work in the morning can be a huge source of joy and gratitude. I also have the business I always dreamed of with my significant other, which is a big thing to be happy about, so if tomorrow were my last day on planet Earth, I would confidently say I lived an overall happy life. I do struggle with letting my thoughts of the future I should have take over though. I sometimes let them get the best of me and it gives me anxiety and even sadness sometimes. I love listening to the likes of Tony Robbins, Ryan Holiday to get me back on track, but I do have to work at it constantly.
Walking is an activity that pays back more than it costs by a long way I feel the same about it as you do.
I think it's important to think about the future, it's unlikely there'll be anyone around or maybe capable of looking after people as they age. Sure, some people have children but with the economic climate I'm not sure how able they'll be to look after parents. (I mean generally here, not you specifically.)
So, I think it's important to think and plan for the future, but that has to be balanced with the present as well because time is a pretty precious and doesn't come around twice.