Spend any amount of time in a dojang and you will see some guy (and it is more often than not a guy) whose moves look, well, clunky. They have a tense stiffness about them, a forced attempt to generate power. Trust me I know I was that guy (and still am on occasions).
Instructors faced with the clunky guy almost invariably say “try to relax”. Of course as soon as anyone tells you to relax you are likely to find yourself completely unable to do so, in fact, you are likely to actually stiffen up more. Akin to the experience of being told not to think of a pink elephant, the first thing that pops into your mind is a pink elephant.