We are living in a fallen world and we are to not love this world as it is temporary.
We are all human and nobody on this earth is perfect. We are born into this fallen world which was shaped and paved by other individual ideas, thoughts, symbols, signs literally leading to physical/spiritual death. The devil/satan is indeed real along with his fallen angel/demonic servants. God sent the devil and his followers (fallen angels) down to earth from heaven to temporarily have his "own" kingdom. The same being who literally hates humanity and will cleverly deceive humanity into destruction. It is in our blood to sin (satan deceiving Eve in the garden) as it is in our human nature. Thanks be to God, Jesus Christ, Yeshua was sent to knowingly die, for humanity to have a chance to be saved from our spiritual death.. sin. This is God's love for us, literally God is love. Our minds can't comprehend the extent of God as he is outside the constraints of time/space and everything we perceive in our human/sinful lenses. When Jesus Christ died on the cross and rose again on the 3rd day, quite literally is when the spirit of Jesus Christ was attainable for eternal life after death. We are saved by the Grace of God.
When we truly believe in God/Jesus Christ, the spirit transforms us slowly over time. God says we leave our past beings, unrepenting human nature, in love with the world; And leave our troubles/worries/fear/needs to God for handling. Obviously and ultimately, God leaves it up to our own free will to have control over our beliefs. Which is why satan/devil/etc has many, many ways to deceive humanity into thinking otherwise. Luckily for us, the truth always comes to light in a world filled with darkness. The devil/satan/etc tries so hard to be like God he will do anything to prove he does not exist, including leading you to believe to "trust/love" yourself... "do what thou wilt" sort of speak.
Regarding Marijuana, to me it's as comparable alcohol, cigarrettes, or even food. The key word I would use is moderation and not over indulge in anything. Best thing to do is to talk to God about these questions. God reveals all things to those who truly seek him through prayer with repentance. It is through the Spirit of Jesus Christ we are able to even be acknowledged/talk to God as Jesus Christ is God in the flesh. It is through his spirit, the spirit of truth these things are discerned. Discernment comes from the holy spirit of Jesus Christ. This isn't about religion, this is about a relationship with God through the spirit of Jesus Christ.
Over time, you start to see the bigger picture. We are all born to die. The spiritual realm does exist. There are entities beyond humans in which exist and they are not looking out for our humanity's best interest. There has only been one person in recorded history to ever die for humanity.. yours truly Jesus Christ. The key to life after death and by the Grace of God we are able to attain this key by believing with all your heart Jesus Christ, Yeshua is the King of Kings, Lord of Lords, Our Savior, Redeemer, God in the flesh.
Every knee will bow to Jesus Christ/God but by that time, if you don't understand any of this, then it will already be too late. Your literal eternal life's fate will be sealed. I come to everyone as a friend who encourages everyone to understand, seek God, research all points of view and more importantly see the world for what it is. Time is truly running out. God Bless and Love You All.