Why do both INTJs and INFJs tend to hold grudges, and how can they learn to let go in a relationship?

What are some underrated features on the iPhone that help you stay productive and avoid distractions?
In what ways do ENTPs adjust their typical behavior to engage meaningfully with INFJs, especially regarding emotions?
If you were to put a teenager in a life-or-death situation, is there a chance they'll get the giggles?