The more Jason thought about refusing to enter Kinra Island, the less likely he was to overcome the dangers that were bound to occur at any moment.
It was because the lands of Inheritances was a great opportunity for him, and evidently also for others.
There were dangers on Kinra Island too, but that was only obvious because nobody would give up on their chance to enter the Inheritance sites, while it was likely to be even more difficult to overcome the trials to obtain an inheritance.
However, with the Mythic Essence cultivation technique, Jason knew that his combat prowess could increase tremendously, even if he wouldn't find or search for an inheritance.
With that in mind, he knew that it shouldn't be too much of a difficulty to cultivate while simultaneously walking around with Jennifer, who could protect him.