Fetching details from the dictionary...

to one's heart's content; as much as one wants; as hard as one can; with all one's strength; to the best of one's ability; to the utmost; with determination; hard; heavily
resolution; decisiveness; determination; resignation
休みの日は思いきり体を動かしたい。
On my days off, I want to exercise to my heart's content.
思いきりボールを投げたら遠くまで飛んだ。
I threw the ball as hard as I could and it went far.
カラオケで思いきり歌ってストレスを発散した。
I sang at karaoke to my heart's content and relieved stress.