Like others here, I'm inspired less by the 'great and the good' of elite performance, but more by anyone who gets out there and 'gives it a go'. There is nothing better than seeing someone bursting through a moment of self-doubt or achieving a previously unattained goal.
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Another and rather strange source of inspiration comes from Sally one of my 2 dogs. Sally is a lurcher/german shepherd cross (didn't quite get THAT piece of information when we got her as a pup from the rescue centre

), and just at the time I started running she went lame. After a couple of vet visits she was diagnosed with having Osteosarcoma (bone cancer) in her leg, and sadly had to have her right front leg removed.
The way she has coped with this is incredible, only a day or so after the op she was back up on her feet (all 3 of 'em

) raring to go for her walks, even though she was under a strict rest regime. Now she's like nothing ever happened and bounds out for a run round the fields morning and evening (and is still a darn sight faster than Meg my other dog).
It just makes me think that even though she is 'just' a dog, if she can cope with something like that and just get on with life, then surely just a couple of achey legs is no excuse.