Many people believe that candles are more powerful if left burning. But many other people are uncomfortable (and for good reasons, like cats) to leave candles burning unattended.

By leaving a candle burning when you have some fear about it, is undoing whatever good the candle could do. You want to be sure the Spirits do not get too fiery and cause a fire. Also, the candle poured into a glass jar often break, because the wicks are not always in the center of the glass.

The only time to leave a candle burning is if it is in a very safe spot, like in a tub or sink. Putting a candle out does not reduce its power. It may, actually, increase your participation and thereby, increase its effectiveness. Unless it is an unusual circumstance, I prefer to light and relight a candle. 

 Remember, however, when you extinguish a candle, Thank God, Goddess, or Whoever Spiritually helps you with your request, even if you have not seen the results yet.  When you relight it, reaffirm what the candle is for. Always finish all candles; it's a matter of respect. This is discussed further in the section below called, "How soon will my candle work?"

 How soon will my candle work

 It Varies.  Candles may work before you light them, during the burning, when it ends, or a time later.  I had one candle achieve its goal while it was still in my handbag, heading home. Often, you are so clear in your intention, your goal manifests post haste.

Results can also occur gradually during the candle or when the candle completely burns out. It can come at one week, one month, or longer. It could take weeks, months, or years to see the full results.

It depends upon the magnitude and grantability of your request. That is why I suggest that you conquer the steps along the way to achieving your goal, instead of heading for marriage, fame, big cash, or whatever your ultimate goal is. Don't always run to do another candle. Wait. Have faith.  

The magic doesn't end when the flame does. (That is why you can put a Candle out and have it still be as strong). On the other hand, if the request is big, ongoing, or has great obstacles, be persistent and do another candle based on what you have learned with the first one.

Always finish all candles.  As mentioned above, it is a matter of respect.  Even if you have already achieved your goal or feel that the purpose was misdirected, burn it to the end.