The light shines in the darkness and the darkness has not overcome it.
—John 1:5
Walk while you have the light, lest the darkness overtake you: he who walks in the darkness does not know where he goes. While you have the light, believe in the light, that you may become sons of light. —John 12:35-36
It is appropriate to leave a blessed candle in a prominent place in your home or on a prayer table. This reminds us that Jesus, the light of the world, invites us to prayer. During prayer in your home, blessed candles can be used to help you focus.
Candles provide a powerful spiritual ambiance. They can calm the heart and open you to the light of God. Blessed candles can be used during severe weather. Traditionally, Catholics would light a blessed candle during a strong storm, invoking the power of God to protect their home. And as is so often the case, Catholic spiritual traiditions have a practical element: the candle will be useful if the power goes out. Blessed candles are a powerful sacramental to use against evil spirits prowling about. The devil lives in darkness and so the light of the blessed candle invokes the power of God to keep the devil's influence at bay.
Catholics should dispose of old sacramentals in a way that shows due reverence. Sacramentals can be burned or buried in order to properly dispose of them. This honors their sacred purpose and returns them to the earth in a dignified way.