The life of an adventurer has many challenges and it is only natural a cautious adventurer would want to prepare for them. Select one ability score to prepare for the upcoming day and preform an activity that hones it for the challenges ahead.
After you complete the long rest, you gain a Preparation die, starting as a d6. Each time you make an ability check related to your chosen ability score, you may roll the Preparation die and add it to the result. The Preparation die decreases by one step each time it is rolled until depleted (d6, d4,d2, depleted).
You can opt to do this during any watch, and by merit of being awake you will be more alert than sleeping, but you are distracted by your activities, and have a -5 penalty to Passive Perception, and make any Wisdom (Perception) check at disadvantage. This action requires a campfire or other similar heat source.