If I could tell my 26 year old self to get into something, it would be meditation. I started with the Headspace app but I think Waking Up by Sam Harris is better - https://play.google.com/store/apps/details?id=org.wakingup.a....
Most days I do 20 mins first thing when I wake up. With 12 days, you could finish the beginner course if you do 1 session in the morning and one in the evening.