First, God is almighty and nothing is impossible for him. Secondly, he loves us! Yes, he absolutely loves us! So we should feel free to approach him and ask for whatever we want. If what we ask for pleases him, we shall receive it. If not, we shan't and know that we were wrong. At any rate, God would be pleased that we regard him to be our loving Father, as long as we don't intentionally sin against him.