Definition of keep something in in US English:

keep something in

phrasal verb

  • Restrain oneself from expressing a feeling.

    ‘he wanted to make me mad, but I kept it all in’
    • ‘My mother used booze and drugs to deal with her anger and my father kept his anger in.’
    • ‘Usually, I can manage to keep it all in. At most, I’ll let a few tears trickle down my cheeks.’
    • ‘I keep my sadness in, when it probably would feel better to get it out.’