Just be thankful you didn't wake up with a burning sensation when you pee.
I lost the recharger for my Mother's L'il Helper and boy am i getting frustrated.
Just be thankful that your fridge is stocked with a nice selection of cucumbers.
Hey, I just realized that all the cucumbers in my fridge are gone!
Just be thankful they are not there and rotten.
My chest is so tight; I cannot stop coughing!!
Just be thankful your chest is not loose & flabby.
I just said "hello" to someone I'd like to punch in the [censored].
lol, just be thankful you didn't punch them landing yourself in jail or the hospital
I finished reading my book 
Just be thankful you can read at all.
The sky is all cloudy right now.
Just be thankful it hasn't cut out the power
I'm behind on my yardwork
Just be thankful you have a home with a yard 
My MA attempts have all been colossal duds 
Just be thankful that they haven't been exploited.
I just had a great idea and forgot it.
Just be thankful they didn't get published and one-starred.
I have to go summer shopping
Just be thankful I'm not upset about you ignoring my post.
Where is summer? It's like below 60 here.
ooops
(ya its 53F here, but Im in NE Ontario here)
Just be thankful its NOT going to rain all summer like it did
last year.
Hey I have an idea!
Just be thankful you remembered it.
It's not lunch time yet!
just be thankful you dont have to work through it
My computer needs a clean up
Just be thankful it doesn't need replaced.
My cat scratched me while playing.
be thankful you dont have to get a blood tranfusion liek my friend did from it
I have a fluffy white cat with a green eye and blue eye, he doesn't scratch too much but leaves evidence of himself everywhere
Just be thankful he doesn't scratch too much.
My stomach is a little achy.
just be thankful its not your heart aching.
I need to rearrange some furniture
Just be thankful that you don't have to rearragge your furniture to a new residence.
I need a new pair of shoes.
Just be thankful you can actually walk in those
If only I were in college again
Just be thankful you survived your 1st go-around 
I really wish I had more iced coffee. This one is almost empty.
mmmmm love that stuff
be thankful you got to enjoy that one,
I just started another cup of coffee
Just be thankful you have another cup if you need it.
I lost my cell phone charger.
oh that sucks!! be thankful you can afford a cellphone and new charger*
I'm out of here folks!
The name of the game here is to make the complaining person above you "feel better" by letting them know things could be worse. Then share a complaint of your own.
Example:
Poster 1 - My boss is really on my case today and it's pretty annoying.
Poster 2 - Just be thankful that your boss has yet to discover your favorite hiding place (broom closet).
I just stubbed my big toe and it hurts.
So when you reply, tell the poster above you why they should just be thankful and leave a gripe of your own for the next poster.
I'll start:
This morning I woke up with a sinus headache.