It affects people in ways they don't expect. If its sudden (like lottery winning or sudden IPO surge) it can be difficult to process. But it is an important thing to realize that one is processing an exceptional event. Like having a loved one die or a spouse suddenly divorcing you.
Not everyone feels "guilty", not everyone feels "smug." A lot of millionaires and billionaires in the Bay Area are outwardly unchanged. But the bottom line is that the emotion comes from the cognitive dissonance between values and reality. What do you value? What is reality?
One woman I knew at Google was massively conflicted when she started work at Google. She always felt that she would help the homeless folks she saw, if she had more money than she needed. Upon becoming rich (on Google stock value), now she found that she wanted to save the money she had for her future kids education and needs. Was she a bad person? Before? After? Do your kids hate you if you give away their college education to the local foodbank? Do your peers hate you because you could close the current food gap at the foodbank and you don't?
When people tell me they wish they were rich, I tell them to be careful what they wish for.
Edited for clarity.
"Buying more Ocean C'Motion lottery tickets"
So far my lottery tickets are losing money, but it is fun for the same reason buying a Powerball ticket is fun.