Mars in Sagittarius tends to want work with a horizon and a point to it. It comes into its own where there's scale to the task and at least a little visibility. Teaching, law, international trade, sport, journalism, expedition work, politics, mission-led ventures. I often see these people in the role of coach, lecturer or organiser of large events — anywhere the job is to catch others up in an idea and lead them somewhere with it.
Corporate routine, the same tasks going round in a circle, tends to wear this placement down faster than almost anything. After half a year of sameness the person often starts either quietly sabotaging the process or picking fights over nothing — which is usually a signal that the energy has nowhere to go. A good fix tends to be building trips, study or regular project peaks into the work. Without them this Mars goes stagnant, and the drive curdles into irritation.
In their own venture this is a strong placement for anything with an international thread: export, education courses, tourism, publishing, cross-border legal practice. The weaker side tends to be the day-to-day operations and the steady holding-together of a team. A founder with this Mars often sells the idea brilliantly to an investor and pulls people in with ease, yet skims the contracts and lets the small slips through. Pairing themselves early with someone who reads the fine print tends to matter more than any pitch deck.
In my experience, the way these people arrive at what they're after tends to come not in a straight line but in flares: a couple of years of intense work, a breakthrough, a long pause, then a fresh direction. That isn't slackness — it tends to be the natural rhythm of this placement. The useful move is to accept it and stop scolding oneself for 'inconstancy', building the rest and the change of field into the schedule on purpose rather than waiting for it to arrive as a crisis.