Judges 9:4
"And they gave him threescore and ten pieces of silver out of the house or Baalberith, wherewith Abimelech hired vain and light persons which followed him"
In being light in Character and not firm, we set ourselves as traps easy to be caught when temptations come. We can be light and vain when we use vulgar language and swear words, regularly cracking and listening to jokes and conversing with friends who are of this nature which can rub off on us. Sometimes after talking to such persons in the same manner as they are, one could feel some sort of emptiness as if some good virtue left off. We have been called to be sober (1 Peter 1:13), but this doesn't mean we may not have a sense of humour as that would step into our accommodative social life, people may never speak to us if we never smiled. To be sober is to have a disciplined sound mind and character.
Being light also makes one lose an opportunity or become carried away, opportunities to share the gospel and when the gospel is shared in such an environment, our audience may as well take us for granted, taking the word lightly. Sadly, this is common today among genuine Christians (careless speech/unserious conduct/playfulness). Being playful as a habit could run off in our spiritual life too. If we introduce this light nature into our Spiritual growth, you know what happens to it? it will die off slowly until it is lost.
Take a look at these quotes from Leonard Ravenhill
"If we don't keep the fires on the altar, it will go out"
"You are just as spiritual as you want to be"
"DOES IT NOT MATTER TO YOU THAT IF YOU DON'T OBEY GOD NOW, YOU MAY GO BACK FAR BEYOND WHERE YOU ARE?" (Paraphrased )
" We live in a world that has lost its way and a Church that has lost its voice "
People tend to take those things we take seriously, and lightly when we present ourselves as light persons to them. Be sober (1 peter 5:8).
May God give us grace.
Shalom.