Balanced builds are everything.
You need to rethink your playstyle/build if you:
Have so many LRMs that you cannot defend yourself. (LRMs are great, but entirely situational. City maps prove that mixing LRMs with other weapons is key, as cover trumps LRMs, but not direct fire.)
Overheat in less than five salvos, or run out of ammo before you die. (Get more heatsinks, or smaller/less weapons to fit more sinks/ammo. Hot maps like caustic prove that having moderated heat levels is key.)
Have so many different weapons that you cant use them all effectively. (Overfillers beware)
Have so few types of weapons that you can't react in certain situations. (Boaters/2PPC+Gauss beware)
Are too slow to cope with large maps. (Speed is everything, and how you move is more important than how fast. Be smart about where you are going, and the route you take there.)
Die too often. Chances are good, you are too vulnerable. There are certain mechs that simply should not use XL engines. As far as I am concerned, this is anything bigger than a blackjack, but playstyles vary, and I use XLs on my HGNs.)
Playing smart is better than playing blunt. Brains trump brawn, something few men understand. (This is where us girl gamers are at an advantage.

Boats: Have fun being the king of dead idiots, and still a corpse yourself in the end.