I was a couple months shy of my 18th birthday when I wrote mine and had completely forgotten about the letter and was surprised when I recieved a letter from myself in the mail last year. I'm so happy I'm nothing like my 17 year old self anymore and my letter is kept where absolutely no one can see it. Writing a letter to your future self is something I recommend everyone to do though.
In order to do this you must remind yourself of some things. There are no rules when you write a letter to yourself and you must remember not to set any limitations on yourself. Sometimes, even in our private writings we self censor. I do this in my diary all the time and I have to step back and ask myself why but I never have any answers. Anyway, you must be honest to yourself with your letter, don't stop yourself from writing anything, no one but you is going to read it.
There are no content requirements for your letter but try to include as many details about your life at the moment because you will not remember the small things 5 or 10 years on.
In New Jersey we've had yet another snow storm so if you're trapped inside like I am, consider this the perfect thing to do. It's a great reminder that the past wasn't always so perfect like so many of us think it to be. Remember, you can always learn from the past.
17 year old me and my prom date. All ready to go to the senior prom. This was the only photo of teenage me I was prepared to inflict on all of you.