Letter #1: Una joven está muy estresada, no puede concentrarse y se cae de sueño.
This person feel very stressed, distracted, preocuppied, she is sleepy, etc. We can conclude that she has some big problem that is bothering her and that's why she doesn't sleep well, she probably neither eats properly, etc. Let's give her some advice.
1. No sientas pánico en las situaciones estresantes. (Don't panic in stressful situations.)
2. Respira profundo. (Breathe deeply.)
3. Come al menos 3 veces al día, aunque sea poco. (Eat at least 3 times a day, even though it is a little bit.)
4. Lee antes de dormir. (Read before going to sleep.)
5. No evites hablar con alguien que sepa ayudarte. (Don't avoid talking to someone who knows to how to help you.)
All the underlined verbs are examples of are affirmative (2, 3, 4, 5) and negative (1, 6) tú commands. If they are affirmative, we just take the -s from the second person singular:
(tú) lees - you read
lee - Read! (command)
If the command is negative, we have to use the subjunctive mode for the second person singular.
indicative: (tú) lees
subjunctive: leas
negative command: no leas (Don't read!)
You can now try to do the same with the second example.