I read Seneca's letter on good company. This letter discusses that the time you have to spend with others is your free time and it is in your control what you do with it. This idea is represented in the technique of dicotomy of control. In order to avoid disappointment you can control the people you spend your free time with so surround yourself with people in good standing and that you enjoy being around.
I also read Seneca's letter on the friendship of kindred minds. This letter was interesting, I got the feeling it was referring to self denial. Seneca talks about not allowing yourself to be friends with someone until they develop themselves into the type of person you want to spend time with. He says "such a joy is light and fleeting" referring to spending time with someone you love, but when the person you love is the sort of person that you desire them to be then the joy is sustained. This phrase is what made me think of self denial because this technique enables you to enjoy things more and for a longer period of time instead of having fleeting joy.