  In this paper we introduce a localized and relativized generalization of the
usual concept of Fej\'er monotonicity together with uniform and quantitative
versions thereof and show that the main quantitative results obtained by the
1st author together with Nicolae and Leu\c{s}tean in 2018 and with
L\'opez-Acedo and Nicolae in 2019 respectively, extend to this generalization.
Our framework, in particular, covers the sequence generated by the Dykstra
algorithm while the latter is not Fej\'er-monotone in the ordinary sense. This
gives a theoretical explanation why under a metric regularity assumption one
obtains an explicit rate of convergence for Dykstra's algorithm which was
proved recently by the 2nd author.
