(Kadamba Kanana Swami, 01 December 2014, Mayapur, India, Srimad Bhagavatam 6.1.50)
It may be true that some people carry a little more spiritual strength from a previous life than others. But, whatever we have got with us in terms of a stock, is not going to last. It is like money; some may have a little more money in the wallet than others, but if you do not make sure that new money comes into the wallet then even if you have a fat wallet, soon it will be empty. Somehow or other, it goes anyway. So, the point is that in this life, we need spiritual strength so that we can have the conviction to actually take up the challenges in spiritual life. That strength is not just coming from what we got from birth. That strength is what we need to build up and that is the main point; one must collect daivī sampad or spiritual wealth.
Just like someone in the world who is always looking for opportunities to make some money, this way or that way to make money. Materialists are always looking for opportunities. In a same way, a devotee is always looking for opportunities to collect some spiritual wealth because it is that spiritual wealth that is the source of strength. Srila Prabhupada gives that example of placing iron in fire and then the iron will act like fire. So the more spiritual wealth we collect, the more that the result will be that we will be more spiritually strong.