move out of fray for rest and then you can see the energy bars go back up.

heavily armored units like halbs tire easily and require this type of micro.

also, halbs are slow and wouldn't catch anything so don't send them off chasing routers, it'll only tire them out.

2 energy bars usually mean time to rest 1 energy bars is rest ASAP.

halbs are low morale and the morale penalty for fatigue is pretty stiff as is that for losing since you'll experience combat penalties for fatigue too. if you aren't careful, soon the halb is gonna run and it's not going to make it as a slow infantry unit.