why is it so hard to keep momentum

i can have a really good day one day and then the next day if nothing really good happens its fine but if something bad happens i become miserable

like why is my brain only focusing on the bad why cant i remember what good happened and hold onto that feeling longer why is it fleeting

i just want to stay happy why cant my mind just give me that

am i asking for too much? do i need to just suck it up and focus on what needs to get done? i dont know i dont know anythingg

:(