“Whatever we do, therefore, it is the mind that is most important. This is why the Buddhist teachings focus on perfecting the mind. The mind is king, and body and speech are servants which must do its bidding. It is the mind that conceives faith and the mind that conceives doubt; it is the mind that conceives love and the mind that conceives hatred.
So look within and check your motivation, for that is what determines whether what you do is positive or negative. Mind is like a transparent crystal which takes on the color of whatever cloth it rests on – yellow on a yellow cloth, blue on a blue cloth, and so forth. Likewise, your attitude colors the mind, and this determines the true character of your actions, no matter how they may appear. The nature of this mind is not something remote and unknowable; it is always immediately present. Yet, if you look at how it is, you do not find something red, yellow, blue, white, or green; it is not square or round, nor is it shaped like a bird, or a monkey, or anything else. The mind is simply that which conceives and remembers countless thoughts. If the current of thoughts is virtuous, you have tamed the mind; if is negative, you have not.”
Kyabje Dilgo Khyentse Rinpoche - The Heart Treasure of the Enlightened Ones – on Introduction – Collected Works Vol II pp 229-30, Shambhala