First, you have to worry about how long can you hold your breath because Navy Seals do it all the time.
Then, you have to worry about stamina. How far you can run without getting tired. Go for some long jogs after school or something and keep doing it.
You'll be getting more endurance, now you worry about your strength. If you have a punching bag, doesn't matter what type. Then you can hit on that for long periods of time.
Do that until you can't even feel your fingers or hands or whatever. Next, you worry about push-ups and sit-ups and all kinds of workouts that help you with your middle core and shoulders.
Then, after now months of doing this, you should be good. BUT THERES ONE MORE THING LEFT.
Blending in, as if your hunting. Trying to blend in to something is probably what Navy Seals are most known for if you can blend in to anything. Your a true Navy Seal.
Keep doing this until you are sure that you are ready for anything. The End.
The creator of this guide has not included tools
I live in Maine.