Qui-Gon is not worried for him exactly—Obi-Wan has been ready for a long time, at least two years before the Naboo mission—but he cannot shake the idea that Obi-Wan should be with him.
He has lost so much, even in surviving. The medics on Naboo have taken his heart and the Council have taken his Padawan.
Source: A Second Heart, by LuvEwan – Star Wars – All Media Types [Archive of Our Own]
A lovely post-TPM what-if, in which Qui-Gon survives but feels changed…