Sweetie, part of your homework is interacting, asking questions. You are BRILLIANT to notice that the impact of a neutral phrase changes drastically depending upon your mood.
The best thing I can recommend if depression dogs you is that “Morning Ritual”–10-20 minutes of movement combined with emotionalized affirmation, remembering things you have to be grateful for, and imagining the positive results of your actions. If you let yourself “get into it” you can seriously anchor your positive emotions into your breathing and focus, and start taking control.
Combine with daily meditation for more power. I would suggest simply “listening” to your heartbeat for 10-20 minutes, sitting very quietly. Very very powerful healing practice.
Namaste,
Steve