1. The phrase "first thing" is a superlative expression (referring to the item that precedes all others). When you are referring to a specific, unique item in a sequence or rank, you must use the definite article "the" before the ordinal number or superlative adjective.

1. When referring to the general activity, "stretching" is the more natural and common noun form (gerund) used after "do a little." If you want to keep "stretch" as a noun, it should usually be preceded by "a" (e.g., "I do a stretch").
2. The word "rush" is a singular countable noun in this context (meaning a state of being hurried). Singular countable nouns typically require an article (like "a" or "the") before them. The idiom is "to be in a rush."
3. The comma after "so" is generally unnecessary when "so" is used as a coordinating conjunction connecting two short, closely related independent clauses. The comma before the conjunction ("so") is sufficient.
4. The phrase "in the morning" is used twice ("I'm in a rush in the morning, so I don't have any special habits in the morning."). I removed this to avoid unnecessary repetition.

1. When connecting two independent clauses (sentences that can stand alone) with a coordinating conjunction like "but," a comma is typically placed before the conjunction.
2. I've added the subject "I" to the second clause ("I eat a small snack") to maintain parallel structure and make the sentence clearer.
3. I've replaced "a little snack" with "a small snack." While "a little snack" may refer to the amount of snack, "small" is a more common and descriptive adjective to use for size in this context.
4. The phrase "like some nuts" acts as an example for the "small snack." I've placed a comma before "like" to introduce this non-essential descriptive phrase.

1. The word "Since" is perfectly acceptable here, but it can also imply a temporal (time-related) relationship. The word "Because" more clearly and strongly establishes the causal (reason-based) relationship between having a late dinner and wanting to empty the stomach.

1. When "like" is used to introduce an example or an explanation (like a non-restrictive phrase, meaning the information isn't essential to the core meaning), a comma should precede it. Here, "5-6 pm" is an example of "early."
2. A comma is needed before the coordinating conjunction "but" when it connects two independent clauses (complete thoughts). The first independent clause is "I used to eat dinner early, like 5-6 pm" and the second is "that doesn't work anymore."
3. The original sentence "it doesn't work anymore" is acceptable but ambiguous. Substituting "that" makes it clearer that you are referring to the habit of eating dinner early (5-6 pm) that no longer works with your schedule.