Hell if I could rewind back to 19 there's so many things I would do with the knowledge I have now. It would totally alter the position I'm currently in at my age. I would start online marketing, affiliate marketing, open a "jungle site" store and a few others and be financially independent within 12 to 16 months. Which is all stuff I do now and make well over 6 figures but didn't learn until 40 and the damage was already done. Relationships will come to you the more confidence your lifestyle instills into you, without you looking. Parents will pass away, unfortunately, mine both have but time changes things. It's nothing like the anticipation of losing your parents. It's very painful when it happens and the memories will remain, regardless of how independent you become, but the memories become tolerable. What else? Newtons law, object at rest/object in motion, etc, etc. I would start something immediately, online. Research and you'll be surprised how fast it begins to grow. You'll be looking for a new car and place of your own sooner than you think possible. Relationships will come and go, those will be painful also. It depends on how much fight you have left. At 19 you should still have some. Dig deep!
Love and respect