After graduating from c25k last May and finally hitting 5k in June, I've been--very, very gradually--increasing my distance and speed. I'm not a fast runner, and my first 5k time was 44 minutes, which was only slightly faster than my walking pace.
But with continuous running every other day (minus days for illness/injury/travel), for almost a full year, I finally ran a sub-35 minute 5k yesterday! 34:52! It didn't even feel like I was pushing too hard, and I wasn't exhausted at the end!
It still isn't fast in the grand scheme of things, but it's something that seemed almost impossible only a few months ago. Just like running 5k at all seemed impossible before I started the programme. I may never be sub-30, but I'm a runner!