How often should I pray?

We might (mistakenly) think that repeatedly praying for oneself is to display a lack of faith.
The conviction may take root that God has heard our prayers, and is in the process of meshing our requests in with his great plans for the world, but that other things may have to drop into place first before the desired miracle will come.
To go on asking, we think, is to presume that God may not have heard, or at least not begun to do something about it.
This logic is rarely applied to praying for other people; in those cases, persistent and faithful praying is readily approved as being right.
Consider the teaching and example of Jesus. He consistently taught the need for continuous and persistent prayer until our object is achieved.
Most miracles are missed for want of such persistence.
One of the major reasons for ineffective prayer is that we do not, or will not, press on into what has already been prepared for us. It is in persistence that we truly demonstrate our expectancy, the largest ingredient in our faith that opens us up to receiving from God.
Nowadays, we expect instant solutions, and, as these rarely happen where expectancy is in short supply, we turn away with wistful thoughts of, ‘Maybe one day….’
Having begun to sow seeds of doubt in our own minds, we become even less persistent and less expectant. The downward cycle of doubt into despair (or, worse, to the dismissal of the miraculous powers of Jesus) begins.
To counteract such negativity, if this is your problem, I suggest reading or re–reading the biblical account of Elisha’s dealing with the Shunammite woman, recorded in 2 Kings 4.
That incident, and the healing of Namaan in chapter five, provide powerful encouragement to us, demonstrating that God has always looked with favour on persistent faith and faithful action.
For further reading on this subject see Why is so much prayer apparently not answered? and Will God raise the dead?
See also my book entitled Heaven’s Dynamite.