This has been a great thread with a lot of thoughtful responses.
Few thoughts that came to mind in reading through the posts:
1) Regarding motivation ... I'm not a naturally ambitious or motivated person, especially when it's not something I feel required to do. So, even when a behavior is seen as "good" (good diet, exercise, etc etc), it can be hard to establish a regular routine. Sometimes, forcing myself to do something for that "start-up" period until it becomes habit helps. Getting to the point where, if I don't do the "thing", I'll feel bad. I'm kind of at the point now where, if I miss a couple days of riding (especially the week-day/work-day rides which tend to be over the same roads), I feel that I've missed something and really need to get out. I've tried to think of it as something that's built into my lifestyle - which does take some time to establish.
2) Regarding the stresses in life that can demand our attention - that can be a real challenge. Our family has gone through some very difficult stresses and they are, to some degree, likely to need our attention for the very long term. One thing I try to remind myself when there are things in life that are, no two ways about it, just difficult, is to not let the very hard things "contaminate" all areas of our lives. Not letting the hard things spill over and take away from the appreciation of the parts of our life that are good ... nurture the relationship(s) that are positive, compartmentalize certain activities you enjoy (in my case, riding), or looking for opportunities to have a positive impact on others (sometimes, the really hard things we're going through put us in the position to be of help to others experiencing similar trials).
3) With respect to riding, people have different approaches in terms of riding solo vs. with a group. If you're finding riding with a group isn't working in terms of keeping up, maybe try to find positives in riding solo (even if you may not naturally like riding alone). For me, I prefer riding solo as I don't have to worry about keeping pace with others, but more because it's a time of reflection and thinking things through without any distractions. I find getting out and on the road often helps me think more clearly and in a more positive way.
Not meaning to come across preachy or presumptuous, just a few random thoughts. Best wishes to all!