I'm sick of getting task cancelled with this; at 25% there is more than enough stamina left to COMPLETE the current tile you're plowing, yet it denies you this and forces you to restart the entire tile again. You can't plow more than 2 tiles at once without drinking water, but if it was 15% before it auto-cancels; perhaps even at 20%, you could complete the third tile task. You'd still go through the same amount of water, and have the same stamina drain, but you wouldn't have to stop mid-stamina bar just to take that extra gulp of water just to complete the next task, which wastes time and disrupts the rythym of the project.
I like building roads and trails, and also I like to plant random crops in the wilderness; things that often require single tile plowing by hand, and constantly having this third task cancelled greatly wastes time and adds extra mouseclicks.
I don't mind the stamina drain on this or the usage of water; what I dislike is the fact that I can't complete a third task in a single sitting of stamina because the threshold cancels it prematurely, when you'd still have probably 15%+ after that third task.
Edit: After more thorough study on the subject, a 20% threshold would be much more balanced, and it would still "fix" this issue.