This has been a command coming from heaven consistently for our salvation. There are short prayers you can say pretty much at any time. The 14-word Jesus Prayer is well-known—"Lord Jesus Christ, Son of the Living God, have mercy on me, a sinner." You can almost pray this unceasingly. You can even shorten it down to "Lord, have mercy on me (or the world)." It's your heart's intention that counts, not how you exactly say the words. If the Holy Spirit inspires you, say whatever he wants you to say. Of course, praying doesn't mean praying aloud either, for hearing the words in your own mind is just as good. The important thing is to pray as much as possible for yourself and others, as the future of the world depends upon our prayers.