Two Shots Of Happy, One Shot Of Sad什么意思?

Two Shots Of Happy, One Shot Of Sad什么意思?
matt dusk的一首歌名Two Shots Of Happy, One Shot Of Sad这句什么意思?
我查了很多字典,Shot的所有意思放在这里都不是很恰当
这首歌在线试听：http://www.google.cn/music/album?id=Be93c34bb7e3cb034
第一首就是
全部歌词是这样的
Two shots of happy, one shot of sad
You think I'm no good, well I know I've been bad
Took you to a place, now you can't get back
Two shots of happy, one shot of sad
Walked together down a dead end street
We were mixing the bitter with the sweet
Don't try to figure out what we might of had
Just two shots of happy, one shot of sad
I'm just a singer, some say a sinner
Rolling the dice, not always a winner
You say I've been lucky, well hell I've made my own
Not part of the crowd, but not feeling alone
Under pressure, but not bent out of shape
Surrounded, we always found an escape
Drove me to drink, but hey that's not all bad
Two shots of happy, one shot of sad
Guess I've been greedy, all of my life
Greedy with my children, my lovers, my wife
Greedy for the good things as well as the bad
Two shots of happy, one shot of sad
Maybe it's just talk, saloon singing
The chairs are all stacked, the swinging's stopped swinging
You say I hurt you, you put the finger on yourself
Then after you did it, you came crying for my help
Two shots of happy, one shot of sad
I'm not complaining, baby I'm glad
You call it a compromise, well what's that
Two shots of happy, one shot of sad
Two shots of happy, one shot of sad
非常感谢

两杯快乐,一杯悲伤
SHOT理解为喝酒时候的一小杯