The Discipline of Remembrance
Seek the LORD and his strength; seek his face evermore.
Remember the marvellous works that he hath done; his wonders, and the judgments of his mouth;
O ye seed of Abraham his servant, ye children of Jacob his chosen.
(Psalm 105:4-6)
God is bigger than the present. Actually, so are we, because as members of "the Israel of God" (Galatians 6:16) we are part of a spiritual race that traces its roots to Abraham (and even further). When we call to mind what God has done for His people in the past, we learn about who He is (and also what to expect from Him today), but we also learn a lot about who we are.
Most Christians know the story of Jesus and the Apostles pretty well; but everyone needs a refresher every now and then. But the Gospel is much older than the Gospels: the story of the Church goes back to Abraham, Isaac, Jacob, and their descendants. Too many Christians have a less than passing knowledge of the Old Testament. They don't know their own heritage! In a sense, they don't know their own God.
In most Christians' private prayers, we regularly ask God to give us things we need: to help us to resist sin, heal our sick friends and save our unconverted family, draw us closer to Him, etc. And we read Scripture that helps us accomplish those things. It's also important to make a habit of remembering what God has done in the past, whether or not it directly impacts us today.
Now, I don't know about you, but I can't read the whole Old Testament every month. That'd be a lot of reading and honestly, pretty boring after a while. But the Psalms are like a condensed version of the Old Testament. Psalms like 78, 105, and 106 give us a quick summary of the stories of Joseph, Moses, and other Old Testament heroes. Other Psalms, like 46 and 121, teach us God's character, and others (1, 24, 51) show us how we should approach God in prayer.
Reading through the Psalms every month or every couple of months (which isn't that hard- one every morning and another every evening will do it in 4 or 5 months) keeps the stories of the Old Israel fresh in our minds. It takes our focus off our personal needs and onto God, His character, and what He's already done for His people. And if it's read with the Gospel in mind, especially in a liturgical context where we're reminded every single day that Christ "was crucified, died, and was buried...[and] on the third day rose again," and every week we receive the fruits of Christ's "perfect sacrifice for the whole world," it won't keep us in Israel, but will always point us on to Christ.