[swatcoder]

It gets much easier to do regularly once you do it regularly, and it also gets easier when you learn how to control your pace and effort.

It's hard (for a while) when you're first starting because most of your runs are pushing your limits -- intentionally or unintentionally -- and you can't help associating the runs with having to push and burn out.

Once you practice for a while (and take the effort to learn pacing), the bulk of your runs feel easy and refreshing and so you want to go do them. And the hard runs that you choose to run for limit-pushing become satisfying because you know you're in control of them and can often see progress in your PR's for pace or whatever.

In other words: you just have to stick with it and it mostly happens on its own. (Unless you're just a type-A person and can't learn to pace yourself)