Determinism is the idea that everything in existence follows a predetermined path thereby disallowing the alteration of the future since such matters have already been decided. Free will on the other hand is the idea that you may deliberately alter the path that life has chosen for you through the choosing of your thoughts. It turns out that both concepts have merit since there are both elements of determinism and free will within a vibrational universe.
Determinism manifests itself naturally in the form of a path that you must follow as a result of your past choices. You are always attracting unto you various scenarios that match the vibration which you have already established. This is why the term "like attracts like" is applicable to your life since you are always attracting that which is of a nature like your own. In other words, you are always attracting objects that match your personal vibration which summates to the attraction of a reality that matches your vibration. Therefore, if you continue to make the same choices in terms of selecting your thoughts as you have done in the past, you will continue to attract experiences that are similar in nature to the reality you are experiencing at present since your personal vibration will remain relatively similar to its present state going forward.
This is where free will enters the picture since you always have the option of making a new choice in every moment of every day. The more alike in nature are your thoughts to the state of your present reality, the more extensively are deterministic influences exercising their power over you. Thus, the greater is the difference in the nature of your thoughts from the state of your present reality, the greater is the degree to which you are then exercising your free will. The result of a greater exercising of free will is naturally a more significant change in the state of your reality since the choosing of thoughts that drastically differ in nature from the present state of your reality will result in the alteration of your personal vibration to the same degree thereby giving rise to the attraction of new experiences.
Another way of viewing this phenomenon would be from an emotional perspective. Whenever you are not experiencing particularly powerful emotions, you are at that moment being influenced almost entirely by deterministic influences. Negative emotion in particular is always deterministic in nature too since you would not deliberately choose to think thoughts that produce negative emotion within you, because such thoughts decrease the desirability of your reality. Therefore, whenever you experience any negative emotion at all, you are then being influenced by your past choices.
Conversely, the stronger is the positive emotion you experience in any given moment of time, the greater is the degree to which your free will is then being exercised since the presence of strong positive emotion indicates that your thoughts are then being chosen quite deliberately. For this reason, if you wish to maintain as much control over your life as possible, rather than be influenced by random deterministic influences, you should attempt to maximize the amount of positive emotion you experience by choosing the most desirable thoughts of which you are aware.