It is the providences of God, taken undoubtedly in connection with other sources of information, which indicate, in particular, the will of God; and those providences are revealed, and can be revealed, only moment by moment.
The doctrine of living in the present moment, therefore, or in the state of momentary inward recollection, is founded not only on the necessity of watching against temptation, which is one reason for it, but on the fixed and immutable relation existing between the providences of God and the claims of God upon the human soul.
If we are bound to obey the will of God, and if we can know his present will, which is necessarily the source of present obligation, only in connection with his providences, it is very obvious that there can be no other mode of holy living than that of living by the moment.
Edited from Religious Maxims (1846) CXLIII by Thomas Cogswell Upham. His blog is managed by Craig L Adams and can be found here: http://thomascupham.blogspot.com