It is good, very good, to memorize several psalms and recite them while you are working or between tasks, doing this instead of short prayers sometimes, with concentration. This is one of the most ancient Christian customs, mentioned by and included in the rules of St. Pachomius and St. Anthony.
After spending the day in this manner, you must pray more diligently and with more concentration in the evening. Increase your prostrations and petitions to God, and after you have placed yourself in Divine hands once again, go to bed with a short prayer on your lips and fall asleep with it or recite some psalm.
Which psalms should you memorize? Memorize the ones that strike your heart as you are reading them. Each person will find different psalms to be more effective for himself. Begin with Have mercy on me, O God (Psalm 50); then Bless the Lord, O my soul (Psalm 102); and Praise the Lord, O my Soul (Psalm 145). These latter two are the antiphon hymns in the Liturgy. There are also the psalms in the Canon for Divine Communion: The Lord is my shepherd (Psalm 22); The earth is the Lord’s, and the fulness thereof (Psalm 23); I believed, wherefore I spake (Psalm 115); and the first psalm of the evening vigil, O God, be attentive unto helping me (Psalm 69). There are the psalms of the hours, and the like. Read the Psalter and select.
After you have memorized all of these, you will always be fully armed with prayer. When some disturbing thought occurs, rush to fall down before the Lord with either a short prayer or one of the psalms, especially O God, be attentive unto helping me, and the disturbing cloud will immediately disperse.
There you are; everything on the subject of a prayer rule. I will, however, mention once again that you should remember that all these are aids, and the most important thing is standing before God with the mind in the heart with devotion and heartfelt prostration to Him.
I thought of something else to tell you! You may limit the entire prayer rule just to prostrations with short prayers and prayer in your own words. Stand and make prostrations, saying Lord have mercy, or some other prayer, expressing your need or giving praise and thanks to God. You should establish either a number of prayers, or a time-limit for prayer, or do both, so that you do not become lazy.
This is necessary, because there is a certain incomprehensible peculiarity about us. When, for example, we go about some outward activity, hours pass as if they were a minute. When we stand at prayer, however, hardly have a few minutes gone by, and it seems that we have been praying for an extremely long time. This thought does not cause harm when we perform prayer according to an established rule; but when somebody prays and is just making prostrations with short prayers, it presents a great temptation. This can put a halt to prayer that has barely begun, leaving the false assurance that it has been done properly.