I agree with Chaz, it's a fine line between too much and not enough pressure on the fish. Things happen fast during the battle and experience must take over. One thing I would add is that a high rod position is usually the wrong approach when battling a fish that wants to go airborne. When the line is in the water, there is tension on the fish. What usually happens on a jump when your rod is high, is the fly line comes out of the water and instantly creates slack. When the fish jumps and the line clears the water, slack is created and the fish may become unbuttoned or wrap around your line because of the slack. A high rod position only allows you to do one thing, move the rod towards the fish and allow slack. You cannot tighten up if needed since the rod is at the most far back position, vertical. Also, when the fish is close by, a vertical rod position will cause the rod to bend past 180 degrees and possibly break your rod. Finally, if the fish makes a run towards you, you have no ability to move the rod to take up the slack.
The best rod position is keeping the rod perpendicular the fish during the battle with the rod lower to the water. Maintain a 90 degree angle of the rod to the fish during the entire time. In that position, you are able to move the rod and maintain constant pressure on the fish. When the fish jumps, don't allow the fly line to come out of the water. In a split second, in the 90 degree position, you are able to move the rod to increase or decrease tension, whatever your instincts tell you to do at the time.
Battling a big fish is why we’re out there in the winter freezing in the winter. It’s more fun if you win the battle..at least once in a while. Good luck.