Early on in life, we acquire strong behaviors that seem to work. Failing to see that life is much broader than what a child's view sees as needed, we start to rely on those "strengths", because they get us reliable results!
So we do what we can to develop this strength, as we are highly motivated: strength = survival, in our primitive brain - therefore, it is vital and "I'll" devote my resources to strengthening it.
Because it works, we use the strength in lieu of trying out new things that we might not succeed in.
For instance, "being helpful" can be a strength, but if we use it to bribe people to like us perhaps we need to develop more strengths in the relationship areas.
Note that a strength is alot like a muscle - use it and it develops into being quite powerful. Use only one muscle and don't exercise the others and you'll have one lopsided, malfunctioning body.
Aristotle put forth the idea that a trait or action that is used properly will benefit one, but if it is taken to excess either toward the harmful downside or past the useful upside it is harmful. The Buddha, after trying various disciplines to get to nirvana, decided it makes the most sense to go "the middle way" - not being too ascetic nor being too self-indulgent.
A relevant book is "What Got You Here Won't Get You There", Marshall Goldsmith. It's about business leaders, but it's really about life and getting results in life (and what better venue than to use examples from business, where results are the point of it all!).
The leaders often will have huge strengths they employ to be successful...to this point. But their glaring weaknesses will be their downfall unless they see them and correct them. The forceful leader (strength is forcefulness of personality) who fails to enroll others in the dream and/or browbeats people, for instance, may need to gain the necessary skills or he will fail. The "positive" leader may need to learn how to recognize and deal with reality. The "nice guy" will have to learn how to confront people and still be considerate - and learn how to do it expeditiously before too much damage is incurred.
All of these are true in normal people's lives. And we need to see that we need to become more than a "one trick pony" (or a few strengths person) or we won't be able to do well in life when we need other skills. Trying to use the same strength in lieu of balance leads to getting alot less out of life. Read Balancing Skills And Knowledge To Lead A Full Life.
Basically, we will try to use our strengths because we know (or "believe") that they will work, so we don't try other things that may lead to long term new strengths because we do not want to experience the inevitable failures and mistakes involved in learning. From that strategy in life, we become hugely imbalanced and much less effective in life.