Before revision: Overall, the self-inflating effect of alcohol can increase the drinker's self-confidence and therefore lead him or her to engage in activities or social situations that would normally make her or him nervous or uncomfortable when sober.
After revision: Overall, the self-inflating effect of alcohol can increase the drinker's self-confidence and therefore lead them to engage in activities or social situations that would normally make her or him nervous or uncomfortable when sober.