You can only eat so much Cake
My informant first heard this phrase from his father-in-law, James Wolford, who was a very hard working and laborious farmer. Robert said it to his daughter, Lauren, in regards to her lifestyle at the time. She had graduated from college a few years prior, circa 2000) and had not yet attempted to find a career. She thought she was living the dream because it was like a constant vacation.
To Robert, this phrase means that there comes a time when you can have too much of a good thing, in Laurens case, carefree vacation time. If you are on vacation all of the time, you will soon lose appreciation for it. There has to be some contrast in your life, meaning you must work hard and the vacation should serve as a reward. Additionally, he said it with the implication that she would soon be off the payroll and would have to be financially self-sufficient. This phrase is important to him and he chooses to remember and use it because he lives by it himself. He does not want to retire early because he knows he will eventually get bored of vacation.
The phrases literal meaning parallels its figurative meaning because one can literally only eat so much cake before they get sick or tired of the taste. Too much of a good thing can be bad. If someone vacations all of the time, they will lose ambition, devotion, character, among other things. Work is good for people mentally and physically, and should be rewarded with a vacation.