Mood Swings

I'd been feeling good about myself today.
I even randomly started smiling as I was walking along because I felt so happy.
Then this evening I was chatting with my housemates and I mentioned something about how I wanted to be different by the time I was 21, and the convo got serious and I started reflecting about my life and how I don't feel I've achieved anything and are worried about the future and feel like I'm not making the most of being young, and I got myself rather wound up and now feel quite down.
It's like I go through life laughing and joking, and in the moment I am actually happy, but there's always this undertone of dissatisfaction and self doubt and sometimes I just got on with things but other times it makes me feel bad. It is actually very tricky to put into words how I feel, because it's not like I'm sad and crying all the time but I still wouldn't say that I am actually properly happy.
But I have made progress.
Whereas I used to binge eat when I felt like this, instead I have made plans to get up at 6:45 tomorrow and go for an early morning swim. Some endorphins should make me feel better!