When I started undergrad, a close relative messaged me this quote:
"If you aren't humble, whatever empathy you claim is false and probably results from some arrogance or the desire to control. But true empathy is rooted in humility and the understanding that there are many people with as much to contribute in life as you."- Anand Mahindra
In other words, you will see a lot of arrogance in the world around you. Bragging, berating, belittling...and so on. My only advice to you is to be humble with your classes. A's aren't easy to get, especially at an institution such as UCLA. But with drive and dedication you can do it.
Find people who are equally humble and helpful. Science is a collaborative field, and as such should be studied in a collaborative way. There's always something to learn from other people.
Finally, take care of your health, both physically and mentally. Without these, education simply becomes a pain. You'll have ups and downs, but prioritize the weekly exercise, good food, and hangouts.
Best of luck as you start this long but rewarding journey!