Dear Mr(s). President,
Congratulations on your victory, but what now? The people are scared. People were very invested in this election and now that you have won, your supporters are waiting for you to do great things while your opposers are waiting for you to fail. Keep in mind that you have four years for these great things to happen, so don't rush yourself into it, take the time to plan ahead. My biggest suggestion to you in your years as president is to keep yourself busy with your aides and assistants to keep yourself informed on what you say. A big hit for this election was all the lies the candidates told and how uninformed they seemed. If you can simply go out there and know what you’re talking about, people will put more confidence in you. Be sure to double check yourself before you say something that can ruin you, like when Trump tried to dodge the nuclear triad question or when Hillary deleted thousands of emails. As far as planning ahead goes, just keep in mind that plans never work in the real world as they do on paper. Another thing you should watch out for is the rivalry that was fueled by the election. People don't want to see you waste time and energy on an American citizen for no reason. Another good way to keep yourself on the good side of the American people is to keep yourself on the good side of other countries. I don't mean that you should have to kiss up to every foreign leader, but don't go out into the world with the idea that war has to happen.
People will be asking you to take all their problems and solve them in the next four years but taking on all those problems right away will burn you out very quickly. I suggest you take a day to prioritize all of your duties in a more organized way. Stress, this is the big thing people always think about when they think of all the responsibilities you now have. All of these things will need attention but some of them are going to be instrumental in your presidency. While you are trying to keep a level head, you will have so many citizens screaming, sending messages, death threats and you need to keep yourself as far away from these as possible. No matter how many great things you do, the people will only remember the one bad thing. You have the power to choose what that event is but only to a point. For example, if you get too involved with another person but you think it's fine because you aren't doing anything wrong, people will gossip. These are the kind of things that you should distance yourself from and you won't have to do this alone, listen to the people that are there to help you.
So truly, congrats, but don't think you won now that you're President, people will still look for any and every way to relieve you of your post.