"pursuit of pleasure and avoidance of pain" is the natural state of living things. It is an invaluable drive that has brought about the vast wealth of this society we live in. It has driven people to explore the secrets of the universe and to build amazing things. This drive has been unceasingly pushing us toward a world with less pain and unfairness, with more equity and kindness since the dawn of humanity. That is an admirable quality in my eyes.

Sadness and suffering too, are a natural part of being alive and isnt something we should avoid. If I lost the ability to hike I would be sad. Because thats the appropriate and healthy reaction to losing something you care about. This sadness and suffering is part of the natural process of grief. When I have lost loved ones I have deeply grieved them with my entire being. I have mourned with every ounce of my self and eventually come through the other side able to move on. I would have it no other way. This process does not preclude finding other sources of happiness later but it is important to go through.

That "deeper source of wellbeing" you talk about is the fantasy part. Can you touch it? can you tell it you love it? Can you share it around a table with people you care about?