Believe in the light while the light is present.

John 12:35–36

³⁵Then Jesus said unto them, Yet a little while is the light with you. Walk while ye have the light, lest darkness come upon you: for he that walketh in darkness knoweth not whither he goeth.

³⁶While ye have light, believe in the light, that ye may be the children of light. These things spake Jesus, and departed, and did hide himself from them.