I read this somewhere else, but it's important so I'll talk about it too. "Something that explains everything doesn't explain anything." Sounds a little confusing at first. Let me try to reformulate it a little bit clearer.
Suppose you have an idea that is supposed to explain something. If any observation you make can be fit into this idea, then it doesn't have any actual explanatory power.
Now, let me explain. If something has no predictive power, it has no explanatory power. Because, if it can't tell you what to expect in the future, it can't tell you why something happened in the past. That is, if something has can explain something, it should be able to take the explanation, and apply it to something it hasn't seen the result of.
Something that can explain everything has no predictive power. Because it if explains x just as well as not-x, it gives you no reason to expect one over the other.
This is why falsifiability is so important in science. If nothing can show a hypothesis to be wrong, then the hypothesis "explains" everything. If there were anything that it didn't explain, then that potentiality would falsify the hypothesis. An unfalsifiable hypothesis can't explain anything.