I can assure you that Jim and I have loved until it hurt, and it still didn't cover all of the needs.
Even if foster children haven't been moved multiple times, or possibly abused, or been through multiple schools, to be moved into a new family, learn their ways, eat their food, find their way in the culture of that family, it would still be a difficult adjustment for all involved.
I remember starting my day, all smiles, saying, "It's just You and me, Lord, we will just go through this day together. Around dinner time, I remember thinking, "Don't call me Mother."
We had, and gave much love, we had and used much patience, and we continually trained and took classes to improve our abilities and knowledge, so that we could meet the many different needs presented by each different child.
Love counts, that's for sure, but do your best to be knowledgeable and well supported as you begin your journey as a foster parent.