Lands End is one of my favorite places in San Francisco. A large plot of forest and trails by the coast, I love the space and atmosphere it gives me from within the city. Already going to the parking lot is a great view of the ocean and land formations, but as you continue up north you'll find more interesting coast lines and the Golden Gate Bridge will come into view. Its not a difficult hike (more of a walk) and its an easy way to take your mind off things for a little bit. On a clear day you can see all the way out to the Golden Gate Bridge, and watch cargo ships pass under along the coastline. There are also small pockets of beaches which tend to be enclosed by cliffs.
If you continue walking for an hour or so, you can walk through Baker's Beach to Marshall's beach. From here you'll see the Golden Gate Bridge towering above you really close, and there will be people sunbathing and relaxing on the sand. If you continue north there are cool rocks that you can climb out into the sea, and watch the waves crash right below you.