They can be kept in with your pillow, or kept in your pocket. I find them very useful everyday, especially during a recent stay at the hospital, where i just needed to breathe in the scent to stay calm. It also helped me sleep soundly.
Lavender has well been known to be a relaxant. Its used in soaps, bubble baths, bath salts and teas, and has been shown to be beneficial to relaxing tense muscles, including menstrual cramps.
Chamomile is most often used in teas, in my experience, and has a calming effect as well.
You can use any combination of herbs and essential oils in the mixture, but my absolute favourite oil is anise star oil. It smells like licorice, and you don't need that many drops to blend a sweet relaxing mixture without overpowering the senses.
Essentially the sachet mixture is a potpourri, and i often have a batch resting in my room before its divided and given away.
I hope you enjoy this 'ible and find it useful for your daily needs :)