Advice - Heads Up

Hi all,

I'm a relative novice/new player, and while my overall game is coming along quite pleasingly, I'm having trouble in the latter stages of HU games where I'm dominant in chips (say 2700-300 with low-medium level blinds) and trying to kill the other player off.

What I'm finding is that it's either 's**t or double up' for them, and it's not usually long before my opponent is back to a competitive chipstack, then as blinds rise it becomes more and more of a coinflip. Is this just a normal routine of HU games?

Any tips received would be appreciated!