Good computer security is hard – it requires a lot of technical knowledge, and takes a lot of time and effort … And at the end of the day, there will always still be weaknesses in your system. This means that you should never be lulled into a false sense of security, thinking that you are working on a “secure” system. You can have a more secure system or a less secure system, but there is no such thing as a perfectly secure system.
Adversaries like the FBI and NSA are technologically superior and have immensely greater resources than you do, and will compromise your system if they are determined to do so. But this does not mean that you should do nothing. What you can do is close off the obvious and easy-to-exploit vulnerabilities, forcing them to use more complex, expensive (in time and resources), and error-prone methods to violate your privacy.
While no single individual system can ultimately be completely protected from them, the collective effect of millions of people making it more costly will overwhelm their ability to target everyone (because they can only afford so many computers, so much electricity, so many analysts, etc.) … Whereas, if none of us do anything, it is very cheap and easy for them to spy on everyone. That is a complete lack of concern about security leads to complete and total surveillance. We should not make this easy for them.
While ultimately, the solutions to the problem of mass surveillance are political, not technological, we should utilize any technological methods we can to disrupt their intelligence efforts as we work towards these political solutions.