Whatever you have heard is superstition and has nothing to do with anything.
Candles can be extinguished any way deemed necessary. Candles have a symbolic value and can be blessed. They have a sacramental value and purpose as well but it stops there.
Be careful not to bring superstition into their use. Other religions have sometimes mixed elements of our Catholic faith (like saint candles) to conceal pagan and other non-Christian practices (voodoo).
If you want to increase your spiritual health simply pray the Rosary. You can light a candle if you want but it won't do anything to make your prayer more efficacious.