@rideswithmoobs cracking pic there. I know what you mean about being over-biked on occasion. I really having my rigid MTB to take on easy bridleway routes, it livens things up when the terrain isn't particularly challenging. At the end of the day though, it doesn't much matter which bike or which trails I'm riding, I always have a great time
As far as solo riding goes for me it's OK to do as long as you think about the risks and mitigate those you can e.g. take a first aid kit, charged mobile, let someone know where you're going and when you'll be back, take a map or phone app so you can give a GPS if the sh!t really hits the fan and you need rescuing... and of course, ride a little more conservatively.
At the other end of the spectrum of being sensible, learning to jump is also ace fun

and being able to manual/jump nasty drop-offs has even saved me once or twice when rolling them would probably have resulted in OTB