In a way, I should shut up, because I haven't been running long enough to comment - it's still a new toy for me, in this running incarnation.
But, compared to last, when I was even then appallingly slow, I'm an absolute slug these days. Taking training as serious training would be absolutely awful.
I have learned to value my running for what it is: a jubilant defiance of the gravitational pull of the easy chair. Running clubs won't even have me I'm so slow. I'll never win anything unless its a wooden spoon. But I'm out there, in the sun, the wind and the rain, sweating with the best of them. And stink proud to be so.
Age has helped: within shouting distance of my 50th birthday, I've not got too much to prove any more. It is easier for me now to say yeah, maybe I'm not going to be even good for my age at this sport, but I'm going to take part. I can feel good about a good run same as Ironman.
Only suggestions I might offer: leave the watch at home for a few weeks. Vary your speed (I think the serious guys call it fartlek) so your legs don't get bored, and if poss, run somewhere beautiful.
Good luck! Marj