It depends on how you define striving. Much of what we do “for” God is not what He has asked us to do. When we undertake work which He has not asked us to do, we end up working in our own power and fulfilling human potential rather than accomplishing His work which reveals His power.
The Bible gives us plenty to go on to live a Christian life according to Christian principles. This is fine as far as it goes. The problem is that many simply take their Christian lives no further than this. If this is as far as it goes, “striving”, in the worst sense of the word, is the result.
What I am stressing in the book, is action coming out of a continual intimate relationship with our Father [action proceeding from relationship.] God calls us to work hard for His purposes but He does not call us to work independently of our relationship with Him.
This is trite to say, but my experience suggests many live their “Christian” lives just that way.