Sad feelings come from negative thoughts. When we dwell on negative thoughts, they start to grow inside our heads and take up a lot of space. They become bigger than they need to be, simply because we are feeding them by dwelling on them. Negative thinking usually falls into these categories: self-criticism, being unrealistically worried, thinking like a victim, or perfectionism. Chances are you may be victimizing yourself by feeling sorry for yourself, or you may be overly exaggerating situations which makes you unnecessarily anxious. You may be harsh on yourself, or you may have unrealistically high standards. Do you notice any of these patterns? We all tend to think in these ways sometimes, and it’s usually unhealthy because it leads to sadness or dissatisfaction
You say you have a loving family and good friends, but do you consciously notice these good parts of your life? Do you feed these good thoughts by dwelling on them? Good and bad thoughts can come into our heads randomly, but we can choose which thoughts to dwell on, and which ones to brush aside. Try to feed the good thoughts, focus more on them, talk about them, write about them, share them with others. The more you dwell on good thoughts, the more they will grow, changing your mood from sad to content. It helps to keep a diary of things you are grateful for -every night write down good memories from the day, and keep this diary handy.
It’s normal to be sad sometimes, because we face difficult situations. When you feel sad, validate your emotions by telling yourself it’s okay to feel down, and tell yourself that this will pass. Don’t dwell on it too long though. Take out that diary and read what you’ve been writing: remind yourself of the good things in life. If you dwell on that, it will grow.