We are in the world but not of the world (John 15:19). Hence why we should be separated from the things of the world (1 John 2:15) and as such we are to focus on the things above (1 Tim 6:17). We can separate ourselves by not being equally yoked with unbelievers (2 Cor 6:14, Amos 3:3). We should not ‘walk’ with those that do not share our goals, beliefs and values. As such, we are forbidden to marry them. Avoid false teachers and all manners of sin and we are not to be defiles (1 Pet 1:16). If you are unsure about whether or not what you’re doing is right, check if it glorifies God. You should also check that it does not harm you in any way, that it doesn’t cause your brother to stumble and if you can ask “WWJD” – What Would Jesus Do? (in this situation) and can sincerely say yes, then it is okay. If not, you are to be seperate from those things immediately. God does not like sin; He can’t stand it. (1 Pet 1:6, 1 Pet 2:21, 1 Cor 8:13, Col 3:17, 1 Cor 6:19-20)
Once you are separated unto God, you will find it easier to lead a holy life. You will become more like Christ (Rom 12:2) and the Lord will see you fit to be a vessel for His use (2 Tim 2:20-21). The benefits of being separated unto God far outweights the benefits of the world. For example, Moses who was known as the Pharoah’s daughter’s son refused such title, honor and priviledge to suffer oppression with the Israelites – the people of God – because He realised that being used for God’s purpose and plan outweights all other benefits. He realised that fellowship/partnership with unbelievers would only lead him to be against the Lord as opposed to being on the Lord’s side (Heb 11:24-25). It is best to be sanctified unto God.