Complex sentence: At their lowest ebb, the family had only some potatoes and coffee for their meal; since that day they vowed to commemorate it and evey year, on the same day, shared the same frugal meal.
Split into simpler sentences: At their lowest ebb, the family had only some potatoes and coffee for their meal. Since that day they vowed to commemorate it and every year, on the same day, shared the same frugal meal.