At age 26 in 1688, the amount of speaking engagements started to impact his health. He was frequently subject to fevers. A letter from his father instructed him "...in your earnestness speaking, keep the reins upon it." His impassioned speaking style was well received by his listeners and contributed to his growing popularity. On occasion, he could move his audience to tears. He became a popular speaker and received constant invitations to speak and give lectures. He traveled almost weekly to different cities to speak.