There is one thing which is unattainable because you already have it and there is not question of having to attain it the question of not attaining it does not even arise.
And then gradually we try to extend that love even further. We must be capable of loving all people, unconditionally. Is it asking too much to love an enemy? It may seems like an impossible undertaking, but it is based on a very simple observation; all beings without exception wish to avoid suffering and not know happiness.