Bread dough is left to prove in order for carbon dioxide to form, which in turn allows the dough to increase in volume. However, the gluten structure in the dough needs to be strong enough to keep the carbon dioxide safely within. If the dough is allowed to keep proving then the carbon dioxide creates too much pressure for the dough to withstand and it therefore deflates. The dough will also then not expand when baked and the taste and texture will be compromised.