In practice this card is read for patience, for the correct proportion of two things, and for a process that cannot be hurried without ruining it. Its most reliable single sense is rate: the card frequently turns up when the querent is doing the right thing at the wrong speed.
The second common reading is reconciliation, either between people or between two commitments inside one person. This follows from the vessels: what the card describes is not choosing between two things but finding the ratio at which both survive. That distinguishes it usefully from the Lovers, which is about choosing, and from Justice, which is about weighing.
The third, from the alchemical layer, is the work itself, a long combination whose product is not yet visible and cannot be judged from its current state. This reading is much less common in popular books and is often the one that actually fits.
Waite's reversed meanings for the card run to conflict of interests, competing demands and things that will not combine, which is a coherent negation for once. Readers who do not use reversals get the same reading from an upright Temperance among cards of disorder, and it is worth noting how often the reversal debate resolves this way: the two schools identify the same meanings and disagree only about which mechanism surfaces them. That is a smaller disagreement than the volume of argument about it suggests.
One practical note. Because Temperance so often reads as rate, it is among the most useful cards in the deck for timing questions, and among the least useful for yes-or-no ones. A querent who wants to know whether something will happen and draws this card has usually been told when, and the answer is not soon.