Hello everybody! We have tons of new awards for the new year that can be requested through our Awards System thanks to Antifa Lockhart! Some are limited-time awards so go claim them before they are gone forever...
Xehanort was the one saying this and his aim was actually not to seal Terra's heart but to kick it out so he could control the body without his interference.
It's the same thing Ansem SoD did with Riku in KH 1 when Riku started to resist Ansem's possession.
But unlike KH 1 Master Xehanort failed with this attempt and both hearts got sealed away. When you watch the Secret Ending of BBS "Blank Points" you'll get some hints as to why Terra can resist Xehanort so effectively for the time being.