Water on earth
Earth gives feeling somewhere to sit. Taurus takes what Cancer is experiencing and responds to it practically, with food, money, presence or a fixed routine, and Cancer generally finds that more reassuring than being talked to about it.
In return Cancer gives Taurus a reason to build. Taurus left alone will accumulate comfort without any particular purpose; Cancer supplies the household to accumulate it for. This is a straightforwardly complementary exchange and it is why the combination has the reputation it has.
Cardinal and fixed
Cancer starts and Taurus holds, which is a workable arrangement provided Cancer accepts how slowly Taurus can be moved. Taurus does not respond to urgency, and it does not respond to atmosphere either.
That is the specific problem. Cancer's usual method of raising something is to change the emotional temperature and wait to be asked what is wrong. Taurus registers the change, decides to wait for it to pass, and does not ask. The message never arrives, and Cancer concludes it was ignored deliberately.
The Moon and Venus
Cancer answers to the Moon and Taurus to Venus, and the Moon is dignified in Taurus, which older astrology treats as a genuinely favourable arrangement. The two rulers are on good terms conceptually: one wants to be looked after, the other is good at looking after.
None of that is guaranteed by the sun signs. It depends on where the Moon and Venus actually sit in the two charts, and a Venus in a restless sign or a Moon under pressure changes the picture completely.
Where it grinds
Inertia. Two signs that both prefer security produce a life that stops changing. Neither partner raises the possibility of moving, leaving a job, or altering the arrangement, and years pass in a state neither would have chosen deliberately.
The second grind is the mismatch in how upset is handled. Cancer needs the upset acknowledged before anything else happens. Taurus responds by fixing something practical and considers the matter closed, which Cancer experiences as being managed rather than heard.
Two suns are a starting point
A sun-sign match describes a broad tendency across everyone born in the same weeks of the year. It cannot tell you whether this Taurus is unusually restless or this Cancer unusually blunt.
What decides it in practice is the Moons, which set the emotional rhythm, Venus, which sets what affection is supposed to look like, and Mars, which sets how conflict runs. Comparing those across both charts gives you an account of two people rather than two calendar positions.
Questions people ask about this
Why is Cancer and Taurus considered an easy pairing?
Both want security and neither enjoys upheaval, so they agree about the goal. Agreement about the goal removes a lot of ordinary friction.
What goes wrong most often?
Stagnation. Two signs that both avoid change can leave an arrangement in place long after it stopped suiting either of them.
Why does Taurus miss Cancer's signals?
Cancer raises things by changing the atmosphere. Taurus waits for atmosphere to pass rather than treating it as a message.
Does the sun sign settle it?
No. The Moons, Venus and Mars carry more of the outcome, and two couples with the same suns can differ completely.