How to increase Breath (Stamina)
While you are running/sprinting in the Black desert world your Breath exp slowly increases each distance you travel. The longer you run/sprint in-game the more breath exp you get. If you are in a guild you can purchase a breath exp finto juice called Sweet berry wild juice in the guild manager. Remember that having much stamina helps you not only in PvP but in PvE as well 'cause some skills need stamina in order for your character to cast certain skills.
Leveling stamina with Auto-run/Afk walking and running
The game offers a feature where you can create an infinite loop. This is an example below that I found. The green lines are pathways, it indicates that you have made a loop and now your character will travel back and forth infinitely on the same road. To use this you need to open map (M) and then click ALT + LMB, it'll loop you to your last position and the new position you set.
Stamina per level table
Hope this guide helps adventurers who are new to the game. See you in the Black Desert World !!