Is this common?

There's a girl who this time last year I'd probably have described as one of my best friends but now I really dread being in a situation where I have to talk to her 'cos conversation's suddenly a real effort.

And I've realised the same's true of someone else who I was quite close to for a short while but have now been pretty much avoiding for the last 2 months.

The first one hasn't noticed really (which says a lot in itself) but the second one said something a while back. I reassured her but have since continued to avoid any meaningful contact with her.

Is this unusual behaviour or does everyone do it? Are there likely to be people secretly avoiding me that I'm not aware of?

I mean you can't suddenly say to someone "I don't want us to be friends anymore 'cos we clearly have nothing in common so why should we both waste our time making the effort to maintain the pretence".

Or can you?