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Too many people rush out saying "I'll just go for a 5k run" because that doesn't sound too far, then they sprint the first 500m because that's how they imagine running should be.
I got roped into doing a 6 km 'fun run' through work about ten years ago. Had a cycling event in Italy a week before, so did no running beforehand whatsoever and just relied on my cycling fitness to get me through it. I couldn't walk downstairs without significant pain for about 3 days afterwards and it was a week at least before all the pain had gone.
The next year I did it again, but spent 6 weeks beforehand running twice a week, gradually building up the duration. Had no pain whatsoever afterwards, despite running 3 minutes faster.
Seconded. Too many people try to build up too quickly, especially if they are already reasonably fit from other sports. Too many people rush out saying "I'll just go for a 5k run" because that doesn't sound too far, then they sprint the first 500m because that's how they imagine running should be. After a couple of minutes they're doubled over by the side of the road unable to breath because they went out too quickly... it's disheartening and gives people the impression that they "can't run". Start easier than you imagine and build up slower than you think you need...
Go for a nice long walk somewhere beautiful. Run some segments when you feel like running and walk the rest. Allow yourself to stop and admire the views, learn to enjoy running for running's sake.