It is common to feel a bit "heavy" or sad immediately after writing—much like the soreness after a deep-tissue massage. However, within a few hours or days, most people report a sense of relief, better sleep, and a "lighter" mental load.
State a feeling ("I feel anxious"). Ask "Why?" and write the answer. Ask "Why?" again to that answer. Repeat five times to find the root.
Forget grammar, spelling, and syntax. If you run out of things to say, redraw the last line or write "I don't know what to say" until a new thought emerges.
If you want to try the clinically studied approach, follow these rules for :