This is not that hard to do and can happen naturally without overthinking it. I used to do a variation of this when I was single. I used to eat the eat the same breakfast (blended milkshakes with fruits/green veggies) and the same dinner (salmon/slice of bread with tomato and walnuts). The key was

a) Eat to live instead of living to eat

b) Being too lazy to commit more than 5-10 minutes for food preparation.

c) Being single where I could own my decisions and "weirdness".