If you're sad or depressed right now, it may cause you to feel more peevish than normal. Your lack of interest or motivation will affect the daily activities you enjoy. Your thinking is affected and, obviously, you'll have difficulty concentrating and remembering things. This will also have an impact in your decision-making daily. And if there are changes in your appetite and sleep habits without much activity, you'll likely experience sickness and fatigue.
Depression may lead you to harmful thoughts, cause you to lose touch with your loved ones, drop out of school or lose a career. A more than two-weeks of situational sadness is depression already. So don't let those feelings of hopelessness, emptiness, and worthlessness control you. If you are experiencing the symptoms above, seek help and get your feelings out.
Talk to someone who will listen and understand you.