In this letter, Jude warns Christians everywhere about ungodly false teachers, similar to the warnings in 2 Peter. While the first two-thirds of his letter is devoted to a lengthy description of such teachers, their sinful ways, and the judgment that awaits them, the last part is a very straightforward guide on what you (we) can do to "keep yourselves in the love of God."
In verses 20 and 21, Jude effectively says, You! Focus on your walk with God:
"...build yourselves up on your most holy faith;
pray in the Holy Spirit;
keep yourselves in the love of God;
look forward to the mercy of our Lord Jesus Christ that leads to eternal life..."
I think Jude would empathize with any of us for the times we've veered off course in our walk with God. He would understand how it could have happened, but he'd also hold you and me responsible for correcting our course. For Jude, the answer is simple: you, prayer, and God.
If I get winded going up the stairs, one day of exercise isn't going to fix it for me. Only by exercising regularly will I be able to climb those steps without getting winded. Only by exercising regularly will I be able to climb the million-plus narrow and steep steps when the blasted escalator at the Rosslyn metro station chooses not to work! Just as I have to build myself up physically (and I have a ways to go) for the unexpected as well as for daily activities, so must I build myself up spiritually.
One of the things I remember from last year's retreat is the message that we should begin each day by centering ourselves in Christ, that we should take a few minutes each morning to be with Christ in prayer. It doesn't mean you have to kneel down. It doesn't mean you need to use a prayer book. In your own way, just talk to God. Quietly listen. And thank Him.
After encouraging us to help others who have been deceived by false teachers, Jude ends with a prayer of praise to God, "who is able to keep you from falling." And he closes with a doxology: "...to the only God our Savior, through Jesus Christ our Lord, be glory, majesty, power, and authority, before all time and now and forever...."
A beautiful prayer of praise we would do well to pray every day. "....Amen."