Newbish battle/fighting question

I can't seem to find an answer after 25 minutes of search online so I decided to give the forums a shot! ;)

Question:
I've notice that while out in 'the world' if I come across and enemy and TAB to target it while spamming my attack button (since I have trouble telling distance needed to land said attack) I find that hitting my attack key cancels my autorun. Is there something in the UI settings (that I've been unable to pinpoint) that allow me to autorun while spamming my attack key so I continue to run towards the enemy until I actually am able to HIT him? (and land said attack I am spamming?)

I may be too used to other MMOs that shall remain nameless to protect my integrity.