Washington didn't run for his third term because he would have barely made it through for the third term and he died in 1799.
George washington did advise the American citizens to view themselves as a cohesive unit and to avoid all political parties and to issue a special warning to cautious of attachments and entanglements with other nations.
What makes a job of a president so difficult is that they have to attend a lot of meetings and to try to make the country a better place more than in the past as possible. Being a president could be very stressful too and you could get tangled into some situations that you wouldn't wanna be involved in.