This is very true. In the bench, if you are weak in the lock out, do some sort of high board press or other lock out work and a lot of tricep work. If you are weak out of the hole, I would recommend more back work, technique work, and lots of speed work. If you are weak in the mid range, I would go for a 2 board or a floor press and lots of triceps and shoulder work.
Squat and Deadlift work the same way.
For the squat, if you fall forward, you need a stronger mid/upper back and abs. If you lose your arch, you need a stronger lower back. If you are slow out of the hole, you need speed work and stronger legs. If your knees come forward you more than likely have quad dominance and you need to strengthen your hamstrings. If your knees come in, you need stronger hips.
For the deadlift, I noticed a huge improvement in my bar speed off the floor by doing a lot of leg work, especial quads, and fixing my technique (I pull conventional), speed work and form of accommodating resistance helped a lot too. If your lower back rounds, then you need to do more lower back work and ab work should help as well. If you have trouble with the lock out, you should try block pulls (many people say rack pulls don't work as well), and strengthening your glutes and hips.
Find out where your weakness are and what is causing you to fail, then train those weaknesses hard until they aren't a weakness any more.
Do not rely on the same assistance work all the time. Listen to your body. Rotate your ME and DE exercises every 1-3 weeks. If you feel like shit, work up to a max 5. If you start feeling better switch to triples. If you feel great, switch to singles. Eat a lot, and maintain a decent level of conditioning. Find what lifts work for you and which don't. Make sure you always get a thorough warm up in before you start lifting. Perform the competition lifts every once in a while to gauge your progress and re-determine weaknesses. Perform speed work at 50-60% of 1RM.
Most lifts have a sticking point. The two best ways to get over it is to get stronger around the sticking point, and to make the bar move faster so you have enough momentum on the bar to move past that sticking point. Speed = power.