Never leave them open.
Not even for twenty minutes when you pop out to the shop.
Never mind that you lived without gates for a year or two without any trouble, or that you could leave them open for the next year and nothing untoward would happen.
The front turf is deeply dimpled. The flowerbeds trampled. A wallflower leans sadly, while a small campanula nearby is uprooted and a branch hangs broken from one of the roses. Mud leads around the side of the house, and the newly emerging grass in the back wears tracks across it and back again. I haven’t dared investigate the back borders too closely in case we have lost any plants; there are certainly a few holes in the unplanted area. I feel utterly dismayed, and very cross with myself.
They must have moved the cows while I was out and the gates stood open. Never again.