Ruled by two benefic planets, Venus and Jupiter, their main objective is to form an enjoyable sexual relationship, with a primary goal to make each other happy. The seriousness of Libra linked to its exaltation of Saturn will give their entire relationship endurance and stability, while their ruling Venus working together with Jupiter, gives enough romance, sexual desire, tenderness and might lead them to a fairytale ending.
This combination of planets forms Neptune in a way, and speaks of the growth of satisfaction leading to orgasmic pleasure, even though both signs might not seem at all sexual to some other members of the zodiac. They can both go to extremes, either having unrealistic faith in each other or mistrusting every word and every action that is made.
The only way to keep the image of trust for these signs seems to be to always stay in a fairytale, unrealistic state, and this is something a Sagittarius will never want to do. As soon as they start their search for something different, Libra will sense the change and become frustrated by their inability to create oneness with a partner they love. The main problem that will eventually surface and need to be dealt with, is in the forces of their Suns.
Sagittarius has too much fiery energy in their Sun, active, taking action and always prepared to give some of it even if nobody asked for it in the first place. This could lead to a subtle, hidden, will imposing and a character shift that will leave them both bruised for respect when a light is finally shed on the issue.
It is not easy for any one of them to find love and share it with someone. They are, after all, an Air and a Fire sign. Even though Libra is ruled by Venus, it is linked to the mental processes, social adaptation and communication through its element, while Sagittarius has passionate feelings, but uses their head, spreading their philosophy, more than actually feeling.
When they get together, they seem to be able to find a balance in which both of them use their heads just enough, and give each other enough room for love to be born. This is a bond that gives both partners the opportunity to understand how deep their emotions can go, as beneficent rulers make way for feelings to surface in a supporting atmosphere. Even though their relationship is not always meant to be the one they will stay in for life, it could prepare them for a love they seek, giving them a glimpse of what they are capable of.
This leads to shared value of their entire relationship and an intellectual understanding that gives them room to build their shared philosophy. Libra wants to stick to their usual routine, and make fieldtrips to things that interest them from time to time.
Sagittarius wants to move from any routine and live a life travelling the world. There are exceptions to this rule, of course, and there are uplifted Libras that will want to travel the world, as much as there are Sagittarius representatives that want to follow a certain trail, while fantasizing about their reality.
This could easily lead to a struggle for supremacy and a battle to reach the ruling position among them. The only way for them to be happy together, is to respect each other fully and let each other do what they are meant to do. Libra should stick to their relationship and love, ruled by Venus, while Sagittarius should stick to their convictions and width, ruled by Jupiter, multiplying the love Libra provides.