to do (something) too much; to overdo an action. Often used as (verb stem) + しすぎる to indicate excess.
心配しすぎると体に良くないよ。
Worrying too much isn't good for your health.
勉強しすぎて目が疲れた。
I studied too much and my eyes are tired.
運動しすぎると逆に体を壊すことがある。
Exercising too much can actually harm your body.
仕事をしすぎて休む時間がない。
I work too much and have no time to rest.