Hanuman was mischievous in his childhood, and in some cases teased the meditating sages in the forests. Finding his antics unbearable, but noticing that Hanuman was but a toddler, the sages placed a moderate curse on him by which he became unable to keep in mind his individual means https://www.youtube.com/watch?v=6cAOQp6Twlc&t=7s