Stress. It's a big part of life here at UCSD. While some of our stress as students isn't avoidable (OChem, Math 140), some of it can be with some smart planning and positive thinking.
Knowing the causes of stress.
If you know that one class gives you more trouble than another and homework takes you longer, plan out more time to devote to that class.
Doing things to eliminate or reduce stress.
Can't stand to be in your room one more second studying? Getting out and exercising has more than one positive benefit.
Managing stress-inducing thoughts. Jumping to conclusions is a good example of making negative assumptions, even if there are are no facts supporting the conclusion. Paying select attention to negative things and ignoring the positives is also a harmful way of thinking.
Paying attention to and reducing negative emotions. Thinking "I'm going to fail this test" is not only unhelpful to you emotionally, it doesn't help with stress levels to catastrophize things.