Children are people too. They experience the spectrum of emotions that adults do but lack the developmental capacity, skills and experience to deal with them (also like many adults!). Below are links to books on a variety of emotions or difficult situations.
BULLYING & STANDING UP FOR YOURSELF
DIFFERENCE (link to WeNeedDiverseBooks)
LONELINESS & MAKING FRIENDS
MINDFULNESS & PRESENCE
OTHER WEBSITES TO CHECK OUT:
Little Parachutes From their website: “Picture books to help children deal with life’s challenges. Little Parachutes provides a unique and simple way to search for picture books that address situations and issues that young children experience.” This website is a kindred spirit to Heart of Picture Books it seems. It does not seem to have been updated since 2013.