This is from the fourteen mindfulness trainings from Thich Nhat Hanh, also called Thay. You can see them and more related information on the Deer Park Monastery website.

The Fourteenth Mindfulness Training: Right Conduct (for lay members)

Aware that sexual relations motivated by craving cannot dissipate the feeling of loneliness, but will create more suffering, frustration and isolation, I am determined not to engage in sexual relations without mutual understanding, love and a long-term commitment. In sexual relations, I must be aware of future suffering that may be caused. I know that to preserve the happiness of myself and others, I must respect the rights and commitments of myself and others. I will do everything in my power to protect children from sexual abuse and to protect couples and families from being broken by sexual misconduct. I will treat my body with respect and preserve my vital energies (sexual, breath, spirit) for the realization of my bodhisattva ideal. I will be fully aware of the responsibility for bringing new lives in the world, and will meditate on the world into which we are bringing new beings.