Mood swings and meditation

In one moment - usually after conquering a body of material - I am confident that, with another week of studying, I may in fact be able to do fairly well on the test. At pretty much all other times, though, I feel completely overwhelmed and paralyzed by the impossibility of knowing Everything. I need to chill out.

It may be time to start meditating. In the past, I have tried a breathing method of meditation: inhale for 5 seconds, exhale for 5 seconds, and continue that for a minute or however long. I've also talked with classmates who meditate using their stethoscope to listen to their own heart beat. My daily bike rides from school to home are also meditative - a physical release and mental break in cool evening air and under the clear Colorado night sky.

This past weekend, I decompressed by hiking in the Rockies - a major perk of going to school in Colorado. Would it be more beneficial to go on another mental health hike the weekend before my first test in medical school, or should I hole myself up and study the entire weekend?