Dear Smart Girl,
Don't give up. When you raise your hand quickly because you know the answer, others might snicker and call you "four eyes" or "smarty pants". They mean this in a rude way but your glasses help you see crystal clear and being smart is a wonderful gift that you need to harness and use in life. They will call you this because they wanted to answer too and don't know how to vocalize that frustration.
You will be good at math but no one will tell you this is an area you are really good in and you should pursue it. You will think everyone else just gets math and pay more attention to music and artistic endeavors. Pursue those artistic arenas because they will show you how to empathize with others and help you understand how others think and feel is different but not bad. But remember that excitement doing timed multiplication tables and being the first one done? That is a feeling you need to pursue too.
Society will tell you that boys are better at science and math. You don't have to believe this ideology. Sure, you may never love biology because that kid you sat next to in 7th grade ate part of a cow's eye while doing a dissection but that's okay, not all science is bad or icky; that's just that one kid. Just because there are areas of math that seem hard, remember that those hard problems make sense to you in ways others struggle to see. You will find certain teachers open up your mind to how math can be a powerful tool. You are not dumb because you don't "get" proofs - don't give up, because one day proofs will finally make sense to you.
You can love theater and love trigonometry, you don't have to pick the one that is more "feminine" - you can do both because they make you a stronger person.
Dear Strong Girl,
You will speak up and people will call you "bossy". They say this because they want to speak up too. It's easier to call you bossy than it is to explain how they want to be heard too. Being the boss of a company may be a really awesome job so "bossy" isn't as mean as they want it to be. Girls are told to not speak up, but that is an opinion, not a fact. Keep using your voice.
You will find that people will look to you to lead them. They will later not like this and try to push a boy into the leadership role. There are actually many different kinds of leaders and it is not dictated by your gender. Lead those who will listen and learn from the other leaders around you. Remember that leading isn't always telling others what to do, but to make sure everyone is cared for and sometimes that means letting other people's voices be heard.
Boys will tease and pick on you because you are not afraid to speak up. You need to keep speaking up because sometimes what the boys say is only one perspective and someone else might think like you but they may be afraid to speak up. The ones picking on you just can't express their emotions so they will call you names. It's okay to be sensitive to their name calling, but know that you are more than what they call you.
Dear Sensitive Girl,
People may only see your sensitive side and encourage you in that endeavor. As a girl its easy to be told to fit a certain mold. You will find you don't fit that mold very well. They will say that we need more sensitive people in the world and we do, but we also need your ideas and innovation too. You don't have to chose to be sensitive or smart, you can be both. It's okay if people don't understand what you want to pursue, they will understand once you start creating magic.
You will be bullied and it will hurt very deeply. Cry those tears of frustration, loneliness, anger, and sadness. Bottling it up will not help you - it might prevent some more name calling but you need to express those emotions. It is not weakness to show your tears, it is ignorance to not allow yourself the space to cry. Don't listen to those voices that say being strong is to suppress your emotions - there is a lot of evidence that doing that only harms yourself in the long run. So cry sweet one, because someone will come along to comfort you and cry with you. Those people will become your dearest friends.
Someone will tell you that your emotions will hinder your ability to make sound judgments. They are lying; because we always have emotions and we always make decisions and feeling more does not mean you are bad at making decisions. Emotions help you see how others think and feel, and sometimes you need to remember that in order to make a decision that will help the most people. God did not give emotions to girls only and rational decision making to boys only - in the Bible it says "Jesus wept" - that means boys can feel and girls can make decisions. Later in life you will learn about social constructs, ideologies, and institutions to help you see that what we think is gender specific "problems" are really just people perpetuating stereotypes that don't have much evidence of being true at a biological level. But that conversation is for another day.
Dear Younger Me,
You are going to struggle, but that's okay. By struggling we learn perseverance, empathy, and gain a stronger idea of who we are created to be. People will try to tell you not to do certain things, but you can prove them wrong. Being different is a beautiful thing.
You will want to hide your intelligence, emotions, and leadership skills. Don't try to be meek and small, God never meant for you to be tiny. Don't push others aside either, because one day you may need them to teach you something. But march forward using all of your brain, heart, and soul that God has given you. By living into these strengths you have you will flourish.
You will be told that being a girl prevents you from being a scientist or engineer. Ignore them, they haven't seen the A+ you will get in Computer Science or the A in Calculus I.
If nothing else beautiful girl, remember this: you are worthy. You have worth as a scientist or engineer or a president. By being yourself you are worthy. You have all the talent and ability to be whomever you want to be. Being smart, sensitive, and strong are all great gifts to have in whatever job and relationship you enter into. Being a girl is a wonderful thing and it does nothing to stop you from being great in any field. Just as being a boy does not prevent them from pursuing whatever they want to be don't let being a girl prevent you from reaching for the stars. People will try to put you down but that is because they can't quite express their own emotions. Listen, and help them understand that what they feel and what they think is fact are two different things. Its easy to think that what we feel has to be fact and that isn't always the case.
Go be a smart, strong, sensitive person and the world will be a better place.