Abundant thinking is a form of positive thinking. It is about creating a mindset of positive values that allow you to perceive your life as one of abundance, not one of deficit. It teaches you to flip your mental attitude coin from negative to positive and appreciate how much you have in your life to be grateful for.
However, it does not suggest that our gratitude should cause us to stop striving for more and just accept our lot in life; rather it teaches quite the opposite: that by acknowledging how abundant our lives are already, our minds will embrace the concept that the good things in life are potentially unlimited.
Abundant means to be richly supplied; to be over-supplied. This means that we should have no fear of asking for more because we can be confident in its delivery. Abundance is a store that never runs out of its goods.