Cancer and Libra are both signs of Cardinal quality, and this gives them a "cut to the chase" nature, when they get tired of standing in one place. This is why their relationship could start in an exciting, passionate way, even though they are individually not that warm and passionate. It is rare for them to attract each other though. Ruled by Moon and Venus, it is as if they don't have enough masculine energy from any side to spark the attraction between them.
Since Libra is a sign that exalts Saturn, Moons opponent, it seems that what they stand for differs pretty much. Libra needs to advance and set high carrier goals. Cancer doesn't care much about building a carrier, unless they find a job they really love. If Libra partner really loves their job, there is a chance Cancer will understand their ambition and the time spent working. If not, this could be the main reason for conflicts in their relationship.
When we say “conflicts” we should keep in mind they will almost never fight. Both signs don't favor Mars and with it any sort of aggression, and avoid conflict at any cost.
To add to that, Cancer is a Water sign and Libra belongs to Air. Libra is slow in decision making and this might help their Cancer partner to keep up with the usual speed of Air. Still, it will not be easy for them to keep up with a similar pace and find the emotional middle ground.
Do you wonder how to conquer his/her heart? Get tips about Libra here.