Brittany Allen compares a person to the way the speaker likes their tea: almost too hot, always a gamble. Every time the speaker is near this person, there's a chance of getting burned and a hope that it will turn out to be exactly right. At first the person is overwhelming, and the speaker feels a warmth inside that suggests real feeling. Then, like tea left to sit, the person goes cold.
The speaker realises the person belongs to someone else, and blames themselves for letting feelings grow. There's guilt and a kind of resigned honesty here: they decide the two are "not meant" for each other. Still, the speaker admits they would risk the burn again, hoping for that perfect temperature.
The ending turns bleaker. The cigarette image suggests something quick, bright and a little self-destructive that will burn out fast. The mood is wistful and tired, caught between longing and acceptance.