A foul-weather friend is the opposite of a fair-weather friend. A fair-weather friend is your friend when your life is fine, and times are good but they abandon you when you have a problem, lose your
job, etc.
A foul-weather friend is someone who likes to be around you when you are unemployed,
depressed and in the dumps. He/she feels sorry for you, and gets some pleasure out of feeling superior, handing out advice, berating you for having a bad attitude. As soon as you get out of the slump, get a
job, get in shape, get a decent place to live, etc., the fair weather friend is
jealous, and stops speaking to you.
Now that you are not a total loser, the foul-weather friend can'
t stand you.