"Let it go" and "let go of" may seem similar, but they have slightly different meanings and contexts: Let it go: This phrase is often used to encourage someone to release their attachment to something, especially negative emotions, grievances, or situations. It's commonly associated with moving on from past events or forgiving someone. Example: "After the argument, it's best to just let it go and move forward." Let go of: This phrase is more direct and often refers to physically or emotionally releasing something or someone from your grasp or control. It implies actively relinquishing ownership or control over something. Example: "It's time to let go of the past and focus on the present." In essence, "let it go" is about releasing emotional baggage or negative feelings, while "let go of" is about relinquishing control or attachment to something tangible or intangible.

It depends on the context, though usually I feel "let go of it" puts more focus on the object and is a little stronger.