Note that the caster loses health right before the target is resurrected (not at the start of the cast). If caster has 240 health before casting, both the caster and the target will have 120 health afterwards. If the spell is interrupted, the caster will not have lost half of his health.
Combine with a skill that increases your maximum health to resurrect allies with increased health. Generous Was Tsungrai is an excellent ritualist healer choice, because it is bound to the same attribute and heals caster's health loss if dropped.
The term "Flesh of My Flesh" may have been taken from the Book of Genesis in the Bible. The passage relates to God using one of Adam's ribs to create a companion for him, namely, Eve.