Even in love, you're practical and predictable. No butterflies-for-a-day for you, because you aim for a stable partner with the same background.
As Raymott says, there is not an obvious answer for this. However, here's a possibility.
Apparently some people mistakenly believe that butterflies live for only one day. Perhaps your example is referring to this belief and is saying: "You are not interested in a beautiful but brief love affair, like the beautiful, brief life of a butterfly. You are only interested in finding a partner for a long-term relationship."