To one’s (or your) heart’s content means to one’s complete inner satisfaction – until one’s heart is content.
This phrase is first put into print in Shakespeare’s plays and there’s every reason to believe that he coined it. He used it in at least two plays:

Henry VI, Part II, 1592 – Her grace in Speech, Makes me from Wondring, fall to Weeping ioyes, Such is the Fulnesse of my hearts content.

The Merchant of Venice, 1596 – I wish your Ladiship all hearts content.