Develop an Altruistic Attitude

In order to have strong consideration for others' happiness and welfare, it is necessary to have a special altruistic attitude in which you take upon yourself the burden of helping others. In order to generate such an unusual attitude, it is necessary to have great compassion, caring about the suffering of others and wanting to do something about it. In order to have such a strong force of compassion, first you must have a strong sense of love which, upon observing suffering sentient beings, wishes that they have happiness--finding a pleasantness in everyone and wishing happiness for everyone just as a mother does for her sole sweet child.
In order to have a sense of closeness and dearness for others, you first train in acknowledging their kindness through using as a model a person in this lifetime who was very kind to yourself and then extending this sense of gratitude to all beings. Since, in general, in this life your mother was the closest and offered the most help, the process of meditation begins with recognizing all other sentient beings as like your mother.
--from Kindness, Clarity, and Insight by The Fourteenth Dalai Lama, His Holiness Tenzin Gyatso.

How We overcome Destructive Emotions

Distinguishing between constructive and destructive emotions is right there to be observed in the moment when a destructive emotion arises--the calmness, the tranquillity, the balance of the mind are immediately disrupted. Other emotions do not destroy equilibrium or the sense of well-being as soon as they arise, but in fact enhance it--so they would be called constructive.
Also there are emotions that are aroused by intelligence. For example, compassion can be aroused by pondering people who are suffering. When the compassion is actually experienced, it is true that the mind is somewhat disturbed, but that is more on the surface. Deep down there is a sense of confidence, and so on a deeper level there is no disturbance. A consequence of such compassion, aroused by intelligent reflection, is that the mind becomes calm.
The consequences of anger--especially its long-term effects--are that the mind is disturbed. Typically, when compassion moves from simply being a mental state to behavior, it tends to manifest in ways that are of service to others, whereas when anger goes to the point of enactment it generally, of course, becomes destructive. Even if it doesn't manifest as violence, if you have the capacity to help, you would refrain from helping. That too would be a kind of destructive emotion.
--from Destructive Emotions: How Can We Overcome Them?: A Scientific Dialogue with the Dalai Lama

Our Mind is like a Mirror

When we understand the empty nature of our own mind, then the consequences of merit and sin will not be realized. In the state of emptiness, there exists no objective merit or sin.
...The nature of the mind is like a mirror; merits and sins are like the reflections in this mirror; and reflections in no way affect or modify the nature of the mirror. When we are in a state of contemplation, we are living in the condition of the mirror. At the time when all phenomena are exhausted and pass into the nature of reality, then our virtuous and vicious deeds will cause no benefit or harm to us. There is no basis for effect--all limitations, all frames of reference, all solid ground having been eliminated. But if we do not understand the nature of the mind and intrinsic awareness through direct personal experience, it will be a very dangerous situation for us.
Indeed, it is not sufficient merely to understand these teachings intellectually; one must first practice and attain realization from this practice. Otherwise the virtuous and the vicious acts we commit in this life will create and accumulate karma, leading us again inevitably into transmigration. From the present time until we realize the ultimate exhausting of all phenomena into the nature of reality, our behavior must be refined; it must be heedful and scrupulous. Otherwise our view is only so much empty intellectual talk.
--from Self-Liberation through Seeing with Naked Awareness translation and commentary by John Myrdhin Reynolds, foreword by Namkhai Norbu,published by Snow Lion Publications.

Form is Emptiness, Emptiness is Form

We are empty, or rather the matter of which we are composed is empty. But the Dalai Lama emphasized that emptiness does not mean nothingness. Some commentators have been mistaken when they have accused Buddhism of being nihilistic. We believe that the world in which we live is part of a flux, a stream of events. This does not mean it is nothing. Everything depends on everything else. Nothing exists on its own. On account of all the influences that come to bear upon them, things appear, exist, and disappear, and then reappear again. But they never exist independently. Form is therefore empty, by which we mean it is not separate and independent. Form depends on a multitude of different factors. And emptiness is form because all forms emerge from emptiness, from this absence of independent existence. Emptiness exists only to give rise to form. (p.341)
--from The Dalai Lama's Little Book of Inner Peace: The Essential Life and Teachings by His Holiness the Dalai Lama