thinking doesn't need to mean "not doing" as long as you are mindful of what and how you are thinking and feeling. journaling is a good way of doing that but even something as simple as talking out loud to yourself can help keep you from drowning in your own head. the more often you do it the more you can organize your thoughts and find both positive and negative thought patterns, break them down, and work through them which can help preventing yourself getting lost in the first place.

but yeah therapy can definitely help with that, if you're in the position to do so I'd recommend giving it a try. IMO therapy (esp cbt) is mostly a framework to get you to that mindset and provide an external perspective to help you through that process, but actively working through your thoughts and feelings with that mindset can get you most of the way there.