This has been referred to as a practice of massaging the heart muscle. In times of having a difficulty with someone in your life, try this. It has always worked for me with different results each time. Always rewarding!
Bring your body and mind to rest and with your attention perhaps in your heart area, repeat these phrases with a sincere heart.
Practice directing these wishes for yourself, and then for a loved one, for someone who is neutral (a stranger perhaps), and a difficult person. You can use them in whatever order you choose. You could also direct it to just yourself, or just one other, or the whole world of sentient beings.
May I be happy
May I be well in mind and body
May I enjoy peace
May I be safe from inner and outer harm
May I live my life with ease
(replace or add to these wishes as you choose)
End with some silence, just taking in the whole experience.
You can repeat this as you move along with your daily tasks, or right in a difficult situation. Just silently choose to wish well with a sincere heart.
Sometimes your wishes for some people may feel fake or difficult. Pay attention to those. Something in you may need some more loving towards yourself. Go back and send loving-kindness to those parts of yourself that need healing and love. Repeat as long as you like and throughout the day.
I hope you all benefit from this. Do feel free to share your experiences with others and with me.