Why

Why earlier I felt really good about myself I felt motivated.I tidy my room a bit, make plans and generally felf like I was ok and I can get my life together but the next day I feel exhausted, tired and don't feeling like doing anythng. Is this hormonal ? Or I'm just felling tired after work? I don't know but I don't like it. I hate having mixed moods. One day I can feel good with my life[which is rare itself] the other day I feel like shit. 

Why?

And I'm going to end up not doing anything today and I hate being not productive. I don't why I'm like this.