May I suggest that you look for a Dhamma teacher that you like. There are many out there a couple of names that come to mind are Jack Kornfield and Ajhan Brahm. They have talks on YouTube on just about any subject. Many of these talks have got me through difficult times and I still listen to them.

It is just a part of life that bodies change and bodies age. I like to think of “seasons of the body”. Currently I am in Autumn. If I look back at past seasons there have been good and bad times. The great thing about the body getting older is that the mind still works just fine. Inside us and in our mind is where happiness is made. This season of body can be your best season. I will leave a couple links to talks that I think might help you.

Joy and its causes:

https://youtu.be/oZs5RXm__IQ?list=PLMHfUPYJU7oQTMoUhRbfs7Tst1nIXHX16

Depression and anxiety:

https://www.youtube.com/watch?v=4N_jjY7W_fs&t=2065s&pp=ygUiYWphaG4gYnJhaG0gZGVwcmVzc2lvbiBhbmQgYW54aWV0eQ%3D%3D

Remember every little step counts. Be patient and find things that make you feel full of joy.