Encourage one another daily ... so that none of you may be hardened by sin's deceitfulness. Hebrews 3:13 (NIV)
"Mind your own business" is not a Christian phrase.
A church family will help keep you from backsliding.
None of us are immune to temptation. Given the right situation, you and I are capable of any sin. (1 Corinthians 10:12; Jeremiah 17:9; 1 Timothy 1:19) God knows this, so he has assigned us as individuals the responsibility of keeping each other on track.
The Bible says, "Encourage one another daily ... so that none of you may be hardened by sin's deceitfulness." (Hebrews 3:13 NIV) "Mind your own business" is not a Christian phrase.
We are called and commanded to be involved in each other's lives. If you know someone who is wavering spiritually right now, it is your responsibility to go after them and bring them back into the fellowship.
James tells us, "If you know people who have wandered off from God's truth, don't write them off. Go after them. Get them back." (James 5:19 MSG)
A related benefit of a local church is that it also provides the spiritual protection of godly leaders. God gives the shepherd leader the responsibility to guard, protect, defend, and care for the spiritual welfare of his flock. (Acts 20:28-29; 1 Peter 5:1-4; Hebrews 13:7, 17)
We are told, "Their work is to watch over your souls, and they know they are accountable to God." (Hebrews 13:17 NLT)
Satan loves detached believers, unplugged from the life of the Body, isolated from God's family, and unaccountable to spiritual leaders, because he knows they are defenseless and powerless against his tactics.