There's definitely more pressure and the feeling of being under the gun. Don't let it get to you or anything else for that matter. If you lose a good fish don't let it get you down and take you out of the game even for a few minutes. In a tournament time is limited so any time you aren't fishing at 100% you are wasting. Also, a jhoffman said never quit. There have been days where you might hardly catch a thing all day and then within 20 minutes of heading back in you catch 4 or 5. Another word of advice, don't chase other fishermen. People have a tendency to watch other anglers when they aren't catching and they start trying to copy someone they see catch a fish. Just stay confident and stick to what you think is going to catch them.
A few other things to keep in mind; if something can go wrong it will go wrong in a tournament. Make sure you keep everything well maintained to minimize these occurrences. On that note, if you don't normally carry tools or extra fuses, wire, TM prop (and TM prop nut and sheer pins), etc. you need to get a kit together. Hopefully you never need it, but it sure can come in handy if you do. Make sure you pack plenty of water/Gatorade. You will be fishing during the hottest part of the day and you need to stay on your game all day long. You don't want your day to end early because of dehydration and the symptoms that come with it.
For the year as a hole, set some goals for yourself. Make sure they're realistic and not something like coming out and winning every tournament. At the end of the year assess how you did and where you need to improve.
Above all else though, remember you are still there to have fun so make it fun. If you're not catching fish don't be a grump in the boat and make it miserable for one another.
Best of luck to you and your partner! Keep us informed on how you do!