So, you're on a survival server. Fairly okay gear, could be better, could be worse. An okay sword. It wouldn't be too difficult to kill someone.
Unless they had better stuff...

1) You're losing the battle. Leave! It's probably the slyest and sneakiest thing to do, and it'll piss the person off, but if you join after a few minutes, hopefully the person will've left, or be out of range, so you can regen or run away.
2) You're losing the battle. Run away! Run and run and run. Run like Bolt, run like the wind, run like it's the end of work, just run and run and run. If there are no-pvp zones? Run there! If there's water? Run there and try and knock the back! If you have a mate? Hook up with them! If not? Just keep running!
3) You're losing the battle. Teleport somewhere! Spawn, your home, a warp - anywhere! Some tps are instant, others take a good few seconds, but if you have enough time, tp!
4) You're losing the battle. Deploy a secret weapon/distraction! Spawn something, dump a bucket of water, drink a potion, anything to momentarily muddle their brain.
5) You're losing the battle. You've exhausted all options. You're clearly die, and there's only one thing left to do. Plead. Shift, right click your sword like you're teaming, step back and shake your head. Its not often this actually works, but if you've got all to lose, this is all you can use.

Good luck out there.
You're gonna need it...