Arianna Weisman and Jean Smith in the Beginner's Guide to Insight Meditation write in Chapter 5, The Buddha's Basic Teachings: The Four Noble Truths, about "Finding Balance" when one is struggling to be loving and forgiving:
... The Buddha's path ... is to reach out in sincere friendship to alleviate suffering when we can. Our hearts can expand in compassion and companionship to share and hold our own and others' suffering. At the same time, it is important to remain at peace when we are not able to reach out or to help. After you have been meditating for a while, you may feel you should be able to reach out to help others or to hold all your own difficulties with compassion instead of aversion or frustration. If you cannot, you may find yourself faced not only with difficulties but also now with negative self-judgment.
But Insight Meditation does not expect us to always be able to respond with open-hearted compassion. Sometimes we cannot, and that is the way it is. In such instances, we must be cautious not to add negative self-judgments. That phenomenon the Buddha compared to being struck by two arrows. Something happens to cause us pain, such as becoming ill, breaking up with a partner, or losing a job (the first arrow), then we heap self-blame on ourselves, shooting a second arrow right into the first wound. Insight Meditation is seeing ourselves as we are, without judgment.