How can I improve my Running Stamina and my Speed?

You know I am really struggling with this. I obviously increased my stamina over several months but even when I went out and ran 20 miles the days that followed, when I tried to do a couple of miles, it was just as hard. Within weeks of the marathon I could barely run non-stop for a couple of minutes and I'm still struggling to do any kind of distance without walking in between.

I thought there would be a time when I could run, say, a mile, without very much of a problem at all. I see other people running past our house holding a conversation or smiling away like they are really enjoying it but I never get to that point.

I decided to do a little googling to see what I could find out.  There is a great deal on here about the subject.

1)     Running, running appears to be the recurring theme here. It needs to be regular (not 2 days running, 4 days sofa surfing!).

2)     It would appear I have to 'shock my body' every now and then and do something that pushes it.

3)     I must run slow and long or fast and short, not both at the same time.

4)     I need to be running outside - it's harder!.

5)     Diet, needs improving and protein after running.

So, there I have it, it's not rocket science but it is very hard, in a nutshell:

Regular
Occasionally shocking
Slow and long
Fast and short
Out in the open and with good food

Simples!