In my metaphysical studies, sooner or later while following a particular thread, I'll end up with a treatise about surrender. It is one of the greatest acts of choice we humans possess. It is also one of (if not THE) greatest acts of faith.
Practically speaking, though, surrender has very particular benefits spiritually (of course), mentally, and physically. The practice of surrender is basically to release striving--release effort, and to release attachments to outcomes. The reason this is a "practice" is because it is not easy. We habitually attach ourselves to our activities and their outcomes. "Achieving goals" and "making a better life" are all egoic identifications wholly dependent on outcomes.
Many spiritual teachers (notably Leo Babuata of zenhabits.com), promote living a goalless life. The premise is that you are perfect and whole just the way you are, and are here on this physical plane to express that perfection. By embracing the surrendering of goals, a tremendous burden is lifted and you immediately come into the present--away from the future and past--free now to enjoy the journey of self-expression.
The practice of surrender becomes difficult or "complicated" when seemingly outside forces enter your life, such as economic needs, health problems, or emotional situations. These seem to require having a goal of a solution. Instead, by practicing surrender, these events begin to appear as reflections of your inner creations--the results of choices and decisions. Surrendering allows the perception of these choices and decisions. You can now see your creation self at work. Life becomes a painting, a sculpture, a dance--and all you need to do is change it up if you don't like what you see, hear or feel.
I like to surrender to God myself, just because it seems most natural for me, but I don't think surrendering to something is necessary. It is simply the act of surrender that releases you from the grip of ego and welcomes you to the present NOW. The mind stops chattering, the nervous system relaxes; you begin to see situations and conflicts as "small potatoes". It's very comforting, really. We don't need to be in the driver's seat all the time, because our belief that we are is really a red herring. Our life simply flows naturally along until a decision comes up, and by surrendering, you'll find the pending decision answers itself. So all you are really doing is responding to your life, enjoying it, and simply making it more beautiful, loving and kind.