What you are training
The single biggest difference between amateur and professional lyrics is whether they name the emotion or show the thing that produced it. "I miss you" is a label; "your coffee cup is still beside the sink" is a picture, and the listener feels the missing for themselves. Showing takes more words per idea and far fewer ideas per song, which is why great lyrics feel spacious. It is a skill, not a talent, and it is trained by rewriting. This drill hands you a telling line and asks for a showing rewrite, then scores the result on concreteness, sensory detail, and whether the emotion survives without being named. The reveal shows a professional rewrite beside yours. A few rounds change how you read every lyric you love, because you start seeing the pictures the writer chose instead of the feelings they refused to state.
After this drill, the plan: The daily plan pairs this with object writing, so the sensory detail you need for a rewrite is already in the reservoir.