Mashiach can be brought about either through free will or through pain and suffering. When an opportunity arises for Mashiach to come and we fail to bring him, then it brings about even greater suffering. The fundamental characteristic of the Messianic era is the concept of giluy yechido, that the knowledge and understanding of G-d will be such that all people will know of the existence of G-d, the way He exists, His attributes, etc. All other religions will disappear from the earth and the purpose of Judaism will be clearly understood by every person alive at that time. The level of the Messianic era will be greater than the level of Adam before his sin, due to the removal of all the impurity inflicted upon creation.