Most everything you do costs turns. Once you run out of turns there is nothing you can do but wait for more. Turns are regenerated 3 a minute and you can save up to a maximum of 6000.

How much turns are used for certain actions?

Cooking - 5 turns

Farming - 1 turn per picked up item

Fighting - 10 turns

Fishing - 1 turn

Picking up items - 1 turn per picked up item, with a max of 10

Walking - 1 turn

Chopping Wood - 5 turns