Develop a talent for delivering a firm & polite “no” to those things which are not essential.
Learning to say “no” to people will not make them hate you. In fact, there’s a good chance it will garner you respect (provided you’re doing it after careful evaluation of your essential values & goals). To maintain positive relationships, it is best to learn how to deliver a “no” that is polite, but not so polite as to seem soft and open to influence through further pressure.