Verse 2.69: What is night for all beings is the time of awakening for the self-controlled; and the time of awakening for all beings is night for the introspective sage.
Sometimes this verse can be a little difficult to wrap one's head around. I am so grateful that I have had the opportunity to learn from my bhakti yoga teachers or it's quite possible that I would have never understood it!
Krsna is stating that for those who are materially inclined, their priorities tend to be very different than those who are more spiritually minded. That's essentially it. In fact, as we may have experienced, some materialistically inclined persons scoff at the very notion of applying any spiritual principles in their lives. Their thinking is more along the lines of "You only have one life to live, so let me do whatever I want, whenever I want." This type of attitude may unfortunately lead to very selfish behaviour.
Even if we all don't aspire to become sage-like, we can at least become more balanced in our approach to life. By understanding the principles of karma and reincarnation, this gives us impetus to strive for something more. Firstly, it helps us understand that we should plan for the long-term because whatever we sow now through our present actions, we will reap later. In other words, although it is important that we live in the present, we should not base our decisions solely on the promise of immediate gratification.
Secondly, it also encourages us to not just "settle" which is something we've been doing for lifetimes.
We've been settling for short term happiness, putting up with various miseries, and running after temporary objects which we don't even get to take with us when we die. Frankly speaking, it sucks!
That's one of the reasons why the Gita is so valuable to all of us; it teaches us both material and spiritual knowledge. On the one hand, it teaches us how to live in this world successfully while educating us about our real identity. By understanding our real identity, we realize that this is just a stop in our journey. This isn't our real home.