Running etiquette

Had a slightly odd conversation with a running friend today (let's call her R). We were agonising over whether to still do a group run we'd planned on friday or cancel it as another of our friends can't do it. R was worried that she would feel left out, especially since we were all going out together straight afterwards, which got me thinking- can training with someone else mean you are cheating on your running buddy?

I've known someone else (lets call her M) who became used to a running with one person and they always did the same route because M thought the other person liked their routine and didn't want to try running further, or faster, or anywhere different. One day M saw her running buddy with another woman, jogging in another part of town on a weekday morning when M thought she was busy doing something else. She felt like her buddy had gone behind her back, though they had never said they were 'exclusive'!

Running relationships can be quite complicated. When I used to run regularly with someone I would sometimes feel miffed if they went without me, even though they were faster and it was obvious they would need to train alone sometimes. People are usually going to have different training needs and different goals, so why do we find it upsetting sometimes to be left behind? Is it our natural competitiveness, that makes us think our buddy is trying to be better than us if they go running without us? Or is it possibly because it makes us feel like we've missed a training session, which makes us feel guilty, even if it wasn't in our schedule? Perhaps it's only women runners who experience this- I wonder if men do too? It's interesting that not even running is immune from our social complexities!