Honkai Impact 3rd involves taking on all manner of enemies in a variety of different battles. To do this, players need Stamina, and the amount of Stamina you have will dictate how many battles you can take part in.
Stamina will automatically refill at a rate of 1 Stamina every 6 minutes. It can also be purchased using Crystals. You can trade 25 Crystals for 60 Stamina. Finally, there are a variety of items in the game that can refill different amounts of Stamina. These items can normally be obtained as event rewards.
Players can also visit Mei’s for Lunch and Dinner, which will give 30 Stamina at 11 AM and 6 PM. This can be found in the Missions screen.
The max Stamina that a player can hold at Level 1 is 80, but this will increase up to 168 at Level 88. Due to the rate of 1 Stamina every 6 minutes, players can earn up to 240 Stamina daily, as long as they have room to store the Stamina.
This does not mean that excess stamina is lost, as some can be stored in a stamina depot. How much depends on the dorm level. Once this stamina depot is full, any excess Stamina is lost.