Sagittarius is ruled by the planet Jupiter, which rules expansion and adventure. The Archer does not like to be held back — he wants to explore, through travels to distant lands or studies of arcane philosophy texts. You may be able keep up with him by going along on ski trips or discussing world religions. However, it is not advisable to cage him in. If Sagittarius feels trapped, he’ll bolt. He needs his freedom. To use a horse metaphor, he needs free rein.
I understand the thrill is in the chase, but I would advise you to gallop besides him, not to catch him. Because the moment you do, he’s gone.