straight edge
A term and lifestyle originally used by a group of reasonably sensible people who saw what drugs/alcohol/casual sex can do to ruin peoples lives and decided to abstain from these activities.

Since then, it has become incredibly popular with young people who are too ignorant/scared to try new things and wanted an excuse not to.
Minor Threat: "We do not want to destroy our bodies/morals, we will be sXe"
Kid: "I'm too scared to try these new things, if I become sXe, I will not look like such a pussy and may even look like a very sensible person"