I've given a great deal of thought to the concept of "free will" and have determined that there really is no such thing. Logically, all of existence is a matter of cause and effect, and since we have no control over the causes (we weren't even present at the time they originated), we obviously can have no control over the effects.
An easy way to prove this precept to yourself is to look back over your life; see that turning point that changed the course of your future? How many people, how many uncontrollable events brought you to that point? See how you really had nothing to do with the path you trod thereafter?
Another interesting side effect of this train of thought is to realize that everything in the universe is interconnected and influences everything else. A simple exercise: look at what you're wearing, then trace each item (and everything in and on it) back to its origin. You'll find people who grew fiber plants (think sun, climate, soil, etc.) in one place (and you can think about what brought them to that time and place, too), factories and workers in other places from whence buttons, zippers, shoelaces, etc. came, and of course the vast array of geographic areas in which the various items of your attire were assembled. Getting aboard this train of thought will allow you to see yourself as a tiny portion of the immense universe, both impacting and being impacted upon by every other entity, from the sun, moon and stars to the ant queen that just laid a thousand eggs in your front yard.
Tying this into the "no free will" argument is simple logic. All the people and elements that went into your appearance today pushed you to make the decisions you made, totally without your knowledge or collusion. Everything that happened everywhere in the universe today will affect what you do tomorrow. Or in the next moment. And you will have absolutely no control over it!