Interact with your Heroes!
It could get really boring, waiting for your troops to finish. Bonding with your Barbarian King or Archer Queen could really prove to be fun way to kill time and stress.
Give new options like poking them, feeding them snacks (costs tiny bit of elixir, 100 maybe?) and use canned chat to "talk" to them to cheer them up.
It would be something like playing Tamagotchi in bird-eye-view. (Google it if you doesn't know what Tamagotchi is)
[EDIT]
What I came up is, each time you interact with them, you slowly raise an invisible stat called "affection". The more affection, the more happy they are each time you tap on them. Also, this stat will increase chance for them to be temporarily rage spell boosted during raids (maximum 80% of the time).
Still not sure how it should be when they are sleeping