If you don't have a Preservation Box yet and want to avoid losing several items that may decay before you can even use them, don't collect too many of those if you don't plan to use them soon. Only get a small amount of those items for what you need at the moment, and make sure to use them all before they decay. About foods (berries, fish, meat), you can opt for alternative preservation methods (cooking or drying) to make them last longer outside of a Preservation Box.