Toz continued pushing his consciousness out of his body to the point where he feared it might break. He spent the time his mind was recovering, either reflecting on his use of magic or on what he experienced when he sent out his consciousness.
Before he knew it, Toz had already done it several times, with each try allowing him to spend more time outside his body. He also began recovering quicker each time he did it. Soon enough, Toz spent more time with his mind outside his body than he did recovering.
The resistance blocking his mind from leaving his body was practically nonexistent in front of Toz's consciousness. And since Toz didn't feel discomfort while exposing his mind anymore, he guessed it was because his mind had gotten stronger. Repeatedly exhausting and wearing down his mind and then letting it recover had strengthened it, allowing him to tolerate the outside world's pressure better.