There's no way to tell without reading the story. It might be a young protagonist who has to make a difficult sacrifice, or perhaps an older character with a lot of life experience facing a situation where sacrifice is necessary. There could also be multiple characters involved in different acts of sacrifice, each with their own motives and backstories.
As we have no details about the story, the main characters could be anyone. It could be a family member sacrificing for the well - being of the family, like a mother sacrificing her time and energy for her children. Or it could be a stranger who makes a sacrifice to help others in a time of crisis. Maybe it's a character in a fantasy world sacrificing magical powers for the greater good.