You get used to it. I would suggest:

- Keeping with the alliance.
- Keeping behind the alliance.
- Only running ahead for brief moments when you have a lot of mitigation (ie. tank invuln or bubble) to draw the enemy attention at you, then have a plan to get behind the alliance quick.
- Only straying from the alliance if you're reasonably confident you won't run into an alliance of enemies ie. to solo a crystal, defend something from another solo player, click something alone to secure it. Have escape plan.
- Only stray if you're actually good enough to fend off 2-3 enemy players, which is possible.

Now I do understand your struggle because when I started doing Frontline, I just got caught up in the PvP and then my alliance ran off to the objective without me noticing, leaving me to get destroyed. I enjoy the actual killing aspect of PvP, not the objectives, but if you do Frontline you have to focus on the objectives and strategies or you'll get killed.

If you want raw PvP, Crystalline Conflict is about as close as you'll get to it, but in that case you can still only hold out so long against the other 5 players before you need some backup.