Welcome Tin Man,
I am the same, except I don't run, so miss out on those endorphins that you are obviously benefitting from. Exercise is great for mental health.
Have you spoken to your GP about how you are feeling, well...not feeling? You probably think that there is no need to do this, but if you're worried about this now, then prompt action might save you getting deeper into 'the pit'. There is a self test here..search K10.. that gives an indication of where you are at.
Writing here does help in various ways. Obviously, it is a way to get things off your chest. A diary with many benefits! Replies received make you realise you are not the only one. Advice comes from the experience of others and often helps to see things in a different light. Sometimes it can be just one thing that strikes a chord within, sometimes it's an orchestra!
Most importantly for me, reading the stories here makes me 'feel'. Most usually empathy, but a full range of emotions including laughter & happiness. I can feel so strongly for some people that it hurts. I want to reach through the screen and hug or scream or cry with them. I just want to help them so much. I 'feel' for them.
When replying, I recall my experience, and the feelings I had at that time. I am getting back in tune with my 'old' feelings. It is always easier to see things in hindsight.
I have felt numb for so long, that I have forgotten what it is like to feel. Or how to. I have suppresed feelings as a defence strategy, and now it is just the way I am. It has become 2nd nature, a habit. It is safe. It is easier. It is a way to 'cope' with everything. I have unknowingly perfected it.
Not only painful, angry or sad thoughts, but happiness, joy and contentment have also been stifled. It is obvious really. If we could tune out only the negative feelings, we'd end up being a giggling, hysterical laughing mess....( I'm getting a vision of the painting 'The scream' with the sound of giggling accompanying ..it is even scarier?!?).
So in responding to you, I just realised a lot about how & why I feel numb. It IS important.
'Just forget it and move on.' Not healthy. It is suppressing feelings that are better dealt with before they snowball. The inability to feel joy is a hallmark of depression. I'm not saying this is you, but it is easy to see how in time, ignoring the hard stuff can lead to an overall numbness.
It is interesting that we never try to forget the good times.