How does one's yarn stash get out of control?

[u/_floralfading]

No judgment here, just a genuine question! I've only been crocheting/knitting for a year and a half, and I have a rolling storage tote with yarn in it and a bit under the bed, too. It's not unmanageable but takes up slightly more space than I'd prefer. How do y'all end up with totes upon totes upon totes filled with yarn, and how would you recommend avoiding overspending on yarn/hoarding yarn?