It's normal, my dear.
Honestly speaking, I have questioned myself this qn before.
"There are many people who are probably less fortunate than me but why am I crying and thinking I'm going through the worst ?" was what crossed my mind before.
I couldn't find an answer to my qn so I deduced the answer lies with our mindset. Perhaps because we are slightly more pessimistic so we aren't happy despite what we have.
On the other hand, optimistic and less fortunate people lead a happier life.
Crying may not be a bad thing because it is a release of emotions.
I believe when it comes to a point that you can't cry would be worse.
Don't worry.
You're not alone. I am like that too.(:
Try thinking positively/ sleeping when you feel down and wake up with better feelings within you ^^
Pardon my lengthy comment.