Stamina management has always been a major part of this game, and it's still that way, after H&H, only in a bit different way.

As always, it's essential to maintain a rested bonus at all times to give the HP regen, but more importantly, gives the stamina regen to help recover stamina faster.

If you are out doing tasks which drain stamina, and run out of rested bonus, stop what you are doing and build a fire and sit by it until your rested bonus is activated again.

Same concept that has always been a part of Valheim gameplay, however, H&H has changed things slightly where you now need to pay attention to what foods you are eating, depending on what activities you are doing, so, if you are out cutting a lot of trees or mining etc. you need to eat foods which give you a bigger stamina pool to work with and of course keep your rested bonus active.

If you are losing all your stamina on one swing of the pick, then you aren't using stamina foods or maintaining your rested bonus properly.