That is two sentences, not two words

If I were to send a note to my younger self it would be,

Believe almost nothing that you are told, instead watch what people do, because most people are idiots.
Chose wisely who you trust, and who you love, because very few people will put your best interests ahead of or equal to theirs.

Two words? This one is simple for me:

Low carb.

not her

(makes me feel horribly about my kids, but absolutely worse decision of my life.)

Imports rock.

Join Marines

Asperger Syndrome.

Love many
Trust few
Always paddle
Your own canoe

Choose wisely.

I'd actually have three words:

Give Zero Fucks.

...In regards to how much other peoples opinion of you should matter. This has become my motto of late. If only I'd learned this earlier.

I would tell my younger self...
change nothing.
You learn a lot by the mistakes you make and by the people you get to know and wouldn't have it any other way. You would not be the lady you are today without all the experiences you end up having in life.
On a side note.. I could say do not marry the man you had married and ended up divorced with because it was a bad situation but then I would not have my daughters or what I learned from that situation.

Two words? "Stay single."

If I were allowed to elaborate a bit: "Don't live with a woman. Any woman. It works well for some men, but it never will for you."

Quit worrying.

I guess it depends on how young my younger self is.

Two words to myself in high school might be "forego popularity" or "AP classes."

Two words to myself in my college years might be "buy Apple [stock]" or "study harder" or "play less."

Two words to myself in grad school might be "study Statistics" or "learn programming."

Of course, all of those are related to the jobs and the career course that followed.

Like jerry, I have a few "not her" notes I could send out - luckily none that resulted in kids or a lifetime of regret.

And, I'd like to tell my younger self to "visit Europe" earlier or to "study art" or "study literature" or "learn French" earlier than I did.

And "exercise more" is something my aging self would like my younger self to have done more often.

And "wear sunscreen" just seems like good advice.

Of course, most of the experiences I'm telling my younger self to pursue or avoid are a result of my being who I am now - as a result of those experiences. So, if I followed my future-self's advice, I might not be the person I am today (whether that's good or bad depends upon what person I would become by following my own advice).

Be Kinder

Fear not.

"Ignore critics."

Dont argue

OK, this isn't two words; nor is it original on my part. From the "It gets better" campaign:

"It might or might not get better;
but, YOU get better"

start fires

Love always
Hate not
Fuck canoes
Buy a yacht

Bold heart.

Deeds, not words.

Don't buy a condo in 2005.

Sunscreen. Always.

I started at age 20, and have great skin for my age. But I'd love to undo the damage I did in my teens. Other than that, I largely agree with April Quinn. Some of my "mistakes" ultimately led me down unexpectedly good paths.