It's like drowning

Source

I haven't told a lot of people I'm close to about what I experience almost daily mostly because 

a) I think that they won't understand

b) They'll tell me to snap out of it

c) They'll think I'm mentally ill and that they need to tiptoe around me about everything.

d) They'll want to know if something happened or if something caused this.

From my experience, there's no one cause. You may have had a wonderful childhood, you may be surrounded by love, but you're still drowning. All The Time.

What does help, of course, is supporting and non judgemental friends and family who help you come up for air every once in a while.