Adam knew he bade farewell to peace when he left Paradise. On earth he had to face conflict and struggle. No sooner had one ended than another began. He also had to toil to sustain himself. He had to protect himself with clothes and weapons and protect his wife and children from the wild beasts.
Above all, he had to struggle with the spirit of evil. Satan, the cause of his expulsion from Paradise, continued to beguile him and his children in an effort to have them thrown into the eternal hellfire. The battle between good and evil is continuous, but those who follow Allah's guidance should fear nothing, while those who disobey Allah and follow Iblis will be damned along with him.
Adam grasped all of this, and, with the knowledge of this suffering, he started his life on the earth. The only thing that allayed his grief was that he was master of the earth and had to make it yield to him. He was the one who had to perpetuate, cultivate, construct and populate the earth. He was also the one who had to procreate and raise children who would change and improve the world.