1) If fish were your customers that you are trying to catch, you would have to worry about three things: Are you fishing in the right spot. Are you using the correct bait? Are you fishing at the correct time?
In marketing, you are testing a lot of things until you come across that correct combination. Maybe a certain headline is not working (bait). It could be the perfect headline but you are not advertising it in the correct venue (spot). Perhaps your product is seasonal and you just didn't know you missed that season (time).
2) If you are fishing with a lot of people around, it is easier to spot trends and quickly adjust your bait. However, sometimes you tend to get tangled into each other and make each other mad.
There are actually two lessons: If you monitor your competition (like you should), you can easily adjust to the bait they are using or at least understand the market a bit better so you can quickly change. The second lesson is sometimes it's better to have others around you helping (not always!).
3) You can't catch any fish without a line IN THE WATER!
This one is pretty simple. If you are not putting your product out there, your ads out there, you are just not going to catch any new ones. I mean what do you think, they will magically jump onto your hooks from the water?
Good luck and happy fishing (for customers)!