When deciding what to learn, there's a binary decision. Will you focus on a strength or a weakness?
I think many people focus mostly on their strengths because they have a goal of really standing out in something. They perhaps want to avoid being average. It's common to hear people give advice that one should work on known strengths. Parents can be heard advising their children to find strengths and perhaps even base their career or life plan on them. I can understand that - but sometimes that ties ones learning to strong social factors rather than personal factors.
If one is interested in personal growth, then maybe one should seriously consider working on a known weakness or weak points for personal reasons. Maybe others will notice the commitment to shoring up weaknesses and the result can also open up doors.
I started my tech career as a data conversion programmer doing mostly ETL in the electronic auditing industry - working with first accounts payable and then health care claim data and doing reporting in the OLAP envoronment. That has expanded over the years to include database programming for the OLTP eCommerce environment. Along the way, I took up Web Development - creating UI in the browser for database-driven applications. Web Development doesn't look like my primary area of expertise on my resume. However, I want to continue to prove that I'm capable there. I want to do work in this area and expand the skill tree. So, to support that I decided to pursue some certifications outside of my primary area of expertise.
Now that those basic web certifications are in place, I will go back to preparing for the SQL Server 2008 Database Developer certification 70-433 - working on what I feel is an area of strength. After I do that, I plan to work on another Web certification in Microsoft's MCTS in .NET Framework 3.5 ASP.NET Applications which covers exams 70-536 and 70-562.
In College and beyond I've taken interest in working on weaknesses. I've felt like my strengths are in reading and writing, language, critical thinking and writing, humanities - and such. My main weakness is perhaps in mathematics. So nearly every semester of college I took a math class from basic math, algebra, trigonometry, calculus, statistics and so forth clear through econometrics. After college I bought books on math and would complete math exercises on my own time. I'm still not strong in math - and my brain appears to be naturally averse to retaining and thinking in the language of mathematics - but I'm definitely better off for doing it and wouldn't take the effort back. My confidence in math has definitely improved.
I think if a person only focuses on their natural strengths, then one runs the risk of not gaining the kind of breadth of knowledge and ability that many professions in the tech industry and elsewhere require for excellence. It's not often visible or flashy to work on a weakness - but I do think there are long-term rewards and satisfaction awaiting those that are willing to do it.