I'd say feeling bitter is very common, especially if you feel like you're always getting screwed over for one reason or another. But you must always keep a clear head. While others may seem to be getting all these breaks and are happy, they only show you what they want you to see. People don't want others to think badly of them, so they'll hide the bad things in their life which you are also experiencing. Nobody is perfect and nobody is truly getting a real break, and even if they are, breaks only last for so long. Just calm down and let it be.