1. Failure will happen. No matter what you do, no matter how carefully you prepare, something you're counting on will go horribly wrong. If it doesn't you're just as likely to screw it up yourself. Their boarding drone might hit your weapons room, they might randomly hack your shields, or you might forget to stop firing when your best crew members are boarding the enemy ship. There is no reason to dwell on it or mope about it. Stuff will just go wrong. That's life; you just pick up the pieces and move on.
2. Make sure you know your priorities. Sometimes life can get distracting. Problems can pop up and crowd out what is truly important. For example, that your ship is on fire. Or that you turned off your oxygen supply to power your laser cannon. Or that there is a mutant alien insect gnawing its way through your pilot. Make sure that you don't get so caught up with what is happening now that you forget about what is truly important.
3. Persistence is everything. This one relates back to the first lesson. Stuff happens, and things hit the fan on a regular basis. The point is to keep going and not just throw your hands up and surrender. It doesn't matter that your boarding party just blew up; don't hit the reset switch automatically. If you give up every time you hit a rough patch, you're never going to find something worthwhile at the end. And the little things--like the explosion that marks the dead enemy flagship--will make every bit of stubborn persistence worth the work.
4. Everyone can do something useful. There's something for everyone to do. The Rockman you just brought on board may not move very fast, but he'd probably do well against boarders. Your robotic Engi ally might not be able to storm the enemy ship, but all that damage you've been taking could probably use his touch. Don't count anyone out.
5. The Challenge makes it worthwhile. Sure, Normal mode might be hard. Okay, a little worse than hard. Maybe we should be referencing XCOM or Ninja Gaiden here. It sucks to have your ship get blown away time and time again. Maybe you're getting tired of running out of fuel and then having to rely on treacherous Slugs to creep along until the rebels get you. Or it is extra hard to get some of the various achievements that the game gives you awards for doing. If it was easy, you'd forget about it immediately. The challenge you struggle through. makes your victory all the sweeter.