It is amazing what an influence other people have in one's life. Friends' casual comments or their own lifestyle can make us question ourselves, doubting our own judgement and soon we are living our lives for them.
And they don't even care! As Dr. Phil says, "It's like my dad used to say: You wouldn't worry so much about what people thought about you if you knew how seldom they did."
That's it in a nutshell. I see so many people killing themselves because they think they are "supposed to." Purim alone is enough to make one take to the bed, the way it works nowadays.
I went out once with a guy who helped people with their debt, and he said how there are actually families out there who have more than one luxury car and take vacations they can't afford and buy a house that will bankrupt them because, and they weren't even ashamed to admit it, "They have to keep up with the neighbors." Spoiler: the neighbors don't notice either way.
This article breaks down who is the bad money friend and how to deal with them. Interestingly enough, it doesn't make any claims on how to change them, because, that is, after all, out of one's hands. It just teaches how to react to their mishagaas.
It's all in your hands, cookie.