Hi, welcome to th wonderful world of TKD.
The point about accuracy is a good one. Also, breaking requires total dedication. Believ it or not, if you don't do the tchnique completely and fully you can hurt yourself a lot more (like if you pull the technique). It means you have to get used to being able to deliver a full technique, rather than some of the pulled ones you might use in sparring.
Sometimes you might hit that board with the force of an elephant, but fail to break (if you don't believe me, how many elephants have you seen doing destruction demos?). Technique and accuracy are all important, not brute force.
The mind over matter bit comes into it too.
See how well I block your punches with my jaw!!
Supporting everyone saying "nuts to cancer"