go back and forth
一指，行为上的有来有往。例句：Just like friendship. They go back and forth.
另指，思想上的左右为难。例如文中的用法。
flip out
意为失控。有时指因生气而失控，文中指因为太开心而失控。
Hem and haw
意为，支支吾吾，哼哼唧唧，表示犹豫不决，内心矛盾。
例句：He began to hem and haw when I asked about his past.
blow off
意为，吹掉，放出。
例句：It remains to be seen how much that perspective becomes another way for China to let the West blow off steam while it moves coolly ahead.
Give someone high-fives
和某人举手击掌
例句：After scoring, the plays gave each other high fives and cheered.