Depends, honestly. I'll have months where I am pretty happy every day, or I'll have weeks where I will be sad for the whole week. I used to suffer from depression so I know what chronic sadness really feels like, but I try to either sleep it off, be productive, or realize that in the grand scheme of things.. it may be pretty trivial.
I can get sad about a load of things; not feeling secure about myself, feeling as though I should've acted a different way towards someone else, not being productive enough, wishing I had things that I don't have, sometimes I get sad out of frustration of things that are out of my control.. sometimes it is trivial like not being able to find a decent pair of shoes that fit me in this country because I technically wear European size like.. 34.5.. (UK size 2, US size 4.5-5) and the smallest they carry is a UK size 3 (US size 5.5-6, european size 35.5)
Yep.. whoops, I ranted.