When glass breaks, it’s easy to point to the most proximate cause:
The mechanical stress from the rock you saw hitting the glass.
Or perhaps thermal stress from an extreme shift in temperature.
In many cases though, the impact of a hard thing or the sudden change in climate are not solely responsible for breakage. There’s another, less obvious culprit: edge damage.
Edge damage are the little nicks and chips at the edges of glass that are so minor in appearance you might not even notice them if you’re not looking for them. Despite edge damage’s harmless looks though, it’s the concentration of stress around edge damage over a period of months and even years that can compromise and shatter entire glass structures.
To the extent that the occasional impact from an outside force and sudden shifts in ambient conditions are out of your control, the solution to preventing breakage can’t be a resolve to avoid sources of stress.
Alternatively, you can decide that seemingly innocuous edge damage is important to pay attention to. The promise of seeing edge damage early is that you can proactively replace compromised pieces with more resilient ones without having to deal with the dangerous and messy aftermath that follows a shatter.