Whenever people talk to me about running - which happens a lot, because a few years ago they'd never have thought of me as someone who runs! - I'm told that people "run too fast too early".
I had the same problem when I started running. Week 1 of Couch 2 5K is 60 second runs separated by 90 second walks (for about 20 minutes). And every time I heard "run", I shot off like a chubby kid after a distant ice-cream van...
And at the end of week 1, I wasn't sure I could do week 2. All week 2 does is switch it round - 90 second runs with 60 seconds of walking between them. And the end of week 1 was tough.
There's no shame in repeating weeks in Couch 2 5K if you need to, but I had an idea - what if I merely jogged slowly? So I tried the first day of week 2, thinking that if it didn't work I'd repeat week 1.
It worked. :-)
Going slow is good. I'd suggest that you shouldn't aim for distance though - aim for times. Aim to run for 20 minutes. Then 23, 25, 38, and finally 30.
When you hit 30, then look at trying to up your speed - a good goal is 5k in 30 minutes. But you need to be able to run for 30 minutes first!
I'm a year and six weeks into my running, roughly speaking, and I can now do 6k in half an hour. So 6k might be a dispiritingly distant goal - which is why I suggest times.
The other thing is that times are, perversely, EASIER. You can slow down and still make them. Out there on the streets, I like putting hills on my routes - which slows me down. Not a problem though - just a challenge that made me work on pacing.
That's how to take it. You can always slow down, even to a walk if you have to, but you don't want to and try not to.
Oh, and doing 20 minutes on a cross trainer is an advantage. You were warmed up! ;-)
(And I still run too fast too early sometimes. Look at this run from Sunday: http://runkeeper.com/user/philipstorry/activity/195036559
- the pace graph is good when it's low, bad when it's high. It starts off low, and gradually climbs higher as I slow down until a little after the first kilometre...)