Think of something that always opens your heart. It can be anything: an uplifting story or movie, an inspiring song or poem, a glorious sunset, a majestic forest, a beloved friend's embrace, a purring kitten... You get the idea.
Now contemplate it vividly until you actually feel your heart opening. Pay close attention to that expansive feeling in your chest, and try to "memorize" it. (For some, the feeling may be quite subtle at first.)
Repeat this process until you can easily recall the feeling of your heart being wide open.
Next, set the intention that — for one full day — you'll deliberately reach for that open-heart feeling before you do or say anything to your child... every time.
This is not about being "nice." When you want to say "no," say it with your heart wide open and it'll feel like a yes!
Let go of all pre-conceived ideas of what an open heart is. Remember it's the feeling you're reaching for.