During most matches, you will not have a clock within sight so you can know the time remaining in a round. You may or may not get a 10 seconds remaining warning of some type. This means you must develop your internal clock so you will have somewhat of an idea where you are in the round. If the round has had a lot of action, you will probably think the time elapsed is more than it really is. If the round has had little action, it may seem if the round has lasted too long.
Taekwondo America tournaments have 500 to 800 competitors. To finish the tournament in a reasonable time, sparring matches are limited to one one-minute round. I tell students that any athlete can hold his or her breath for 60 seconds; so ideally, one should not even have to breathe during a round. Under fighting conditions, this is not possible, but it does mean that you should be able to throw continuous kicks and punches for the entire round. If the opponent never gets an opportunity to score, he or she will not score. In a one-minute round, there is no time to dance around and feel out the opponent; you just attack. However, in tournaments where rounds are longer and/or more numerous, this strategy will not work; in these tournaments you will have to manage your time and pace yourself accordingly.