It is not necessarily a sin, but it is certainly stupid.
When you are young, death is the thing farthest from your imagination. Young people have a general feeling of immortality. However, you never know what’s around the corner. James Gandolfini is a good example of this. Early on his last day, he took his son to visit the Vatican. We can only hope he made a good Act of Contrition while there. Later, he had a sumptious dinner in a first class restaurant with his son. Afterwards he went up to his room to use the bathroom. When he did not return to his party, his son was sent to see what was detaining his father. Gandolfiini’s son found him unconscious on the floor of the bathroom…it was too late for him by the time the emergency medical team arrived. He was only 51 - which by today’s standards is fairly young to die, and, the number of young people killed in accidents of every kind is not small.
Even though you may be young, is it worth the risk of eternal damnation just to go out for some “fun” rather than confession?