I find it beyond me to understand all of this paper, only that cosmic acceleration is not slowing down, which is IRC against a lot theories. Bouncing universe for one, and a guaranteed heat death. That is if the U does not slow in the near future. https://arxiv.org/abs/1701.04973 The possible slowing down of cosmic acceleration was widely studied. However, the imposition of dark energy parametrization brought some tensions. In our recent paper, we test this possibility using a modelindependent method, Gaussian processes. However, the reason of generating these tensions is still closed. In the present paper, we analyse the derivative of deceleration parameter to solve the problems. The reconstruction of the derivative again suggests that no slowing down of acceleration is presented within 95% C.L. from current observational data. We then deduce its constraint on dark energy. The corresponding constraint clearly reveals the reason of tension between different models in previous work. We also study the essential reason of why current data cannot convincingly measure the slowing down of acceleration. The constraints indicate that most of current data are not in the allowed region.