The 'sacrificing his life' are the all the events leading up to and including an experience of rejection, torture, death which is, for lack of better words, always and forever occuring. Maybe think of it like groundhogs day? Or eternal damnation? Or any other eternal punishment? In this case it's the experience of being rejected, then tortured, then death, all of which the individual has volunteered.
The challenge is, trying to understand that this is an all powerful being, which is adopting these human characteristics, these human death and torture experiences and feeling them just as a human would.
And then, if one applies the consequence of being eternal, then all of these awful experiences are happening continuously without end. Even the last moments where a human would be succumbing to their physical demise, losing concsiousness, everything going black, the fear of the unknown, all of the things that person would feel, if they were hung up by the romans, all of those awful feelings would never end.
It seems that your objection is, "but he rose again, so, it's not a sacrifice of life, because, he could do **stuff** after that", right?
The problem with this objection is that it assumes a linear sequential time-line experience that finite time-bound human would experience. That doesn't work for an eternal being. It's not a linear sequential time-line experience. So there is no 'before', there is no 'after'. Saying "but he rose 3 days later, so there was no sacrifice", doesn't work here. There's no 'later', that doesn't apply here.