My solution was to work fewer hours. I'm down to 4 per day, divided into separate slices. It's easy to hold focus for those individual time periods and the net result is as good or better as trying to focus for 8 hours.

I'm same as you, natural recluse who never feels lonely. I do get out and interact with people but have found that most are so overflowing with negative emotion that being alone is more enjoyable.