My elderly parents were that way for a long time. I told them those feelings of sadness, depression, hopelessness- that is exactly how satan wants you to feel in these times. The most defiant thing you can do is find things in life to smile about, and using that as your foundation, live your life to the fullest by fulfilling your purpose. That purpose is completely unique to you, and is up to you to discover it if you haven't already.

You have a finite amount of time on this earth until you disappear into eternity. If you ever feel like there is no point in doing anything, by the same logic there is no point in not doing anything. Fix your inner world, and grow out from there. You got this, my friend. :)