that next time you will try even harder to complete the task as it should be done. and, if you do complete it give yourself a reward. punishments can be anything from pushups to no sugar. i find what works well for a reward is to have a bigger reward in mind and use a sticker chart system to obtain this. every time you complete a task or finish something on time you get a sticker and once you have a certain amount of stickers you can get your reward. rewards can be anything from a new pair of shoes to a massage.
make sure you take breaks throughout the day. 