Well you can become depressed, you'll do stupid things that affect your social life, one bad decision can ruin your whole entire life, physically you'll feel like h e l l and won't want to get up/out and do things. You'll develop tons of health issues also
Well some social reasons may be, to not get pregnant and embarrass yourself. Some physical reasons being to not catch STD's and hurt your health. Lastly, some emotional reasons being, all the stress you will get if you do get pregnant or catch an STD. All of these can harm any human being. <span />