What you do affects the others. If that something you do happens to be bad, who knows, your deeds might cause the person to commit suicide. That makes you a killer. And from this, it's obvious that you are not contributing to this world but be part of something that destroys this world. You are given a life, and yet you are doing these pointless things. Maybe not so pointless, considering that what you do makes you feel better. But are you really that selfish?
You said you believe in God, but a true believer does not do these things. Because deep down they know what's best for the world; that is not to cause any more harm, that is not harming any other humans, violating their rights to be who they are, who they want to be; destroying other creatures' lives, and self-harming. You are not doing it for nothing, but surely you have realised that by not doing these things are for the better good of the world.
Humans are actually capable of good and bad; but we have chosen the bad ones. Is this really necessary? In reality, everybody is scared and afraid all the time. Afraid to be judged, scared of getting harmed, all the shits we are supposed to give less fucks about. But we have taken them personally, because we are THAT self-absorbed. We only managed to look after ourselves. We make friends because we are afraid of being alone. We wear clothes because we feel embarrassed to be in our naked form. We judge because we expect it to make us feel better. And people believe in God, in actual fact, is because they hope God can provide them with senses of security for THEY themselves. As long as they're safe, they think it's perfectly normal to condemn and harm other people. But you do know that God does not permit human violation, don't you?