Luke 12:3 says, "What you have said in the dark will be heard in the daylight, and what you have whispered in the ear in the inner rooms will be proclaimed from the roofs". Johnny cash sang about this concept his song, "God's Gonna Cut You Down", with the lyrics, "But sure as God has made the day and the night, what you do in the dark will be brought to light".
This reminds me of one of my not-so-shining moments as a middle-schooler. I was gossipping about one of my friends with another girl from school. I was going on and on about this girl. Then I heard in the distance, "Chloe? Hello?" I had pocket dialed the girl I was gossipping about. While I was more humiliated than I could put into words as a 13 year old, the scenario ended up being a great example of this concept. What you do in secret, what you think in secret, what you feel in secret will be brought to the light, if not dealt with.
If you harbor thoughts of jealousy, it will fester into discontentment with your life. If you are holding a grudge against someone and don't take steps towards forgiveness, you will become bitter and cold to others. Feelings of hurt and anger aren't wrong, but when they aren't confronted, you begin to spiral down an emotionally-distraught path that only leads to misery. And it's a lot hard to get off the path once you've been traveling down it for some time. Trust me.
The concept in Luke 12:3 can apply to so many more parts of our daily lives. We must strive to be the person we want to be during all moments of our day. Everything you do, even the things no one really knows, is a component of you are and who you will become. Some things may take longer to manifest into your public life, but sooner or later they will take surface.
Take it from my teenage crisis I shared. Those ill thoughts I had toward my friend turned into a topic of conversation with another person. And unfortunately, those thoughts would end up hurting my friend.
Confront your heart, your mind and your spirit. Always be alert of what you are thinking, feeling and doing in your alone time. It will be brought to light.