The structure of this paper is as follows. My starting point is psychological flexibility (henceforth, PF) as it has been presented in psychology. Here I offer a synthetic view which embraces the most crucial aspects of flexibility, and describes its functional roles and underlying mechanisms. Secondly, I move my attention onto the field of current action theory and discuss two elementary concepts we commonly use when describing our actions: intention and desire. Of course, there are many “theories of desire” and (...) there is no point in trying (nor even the option) to discuss all of them under one heading. To show where the question of PF sneaks into the scene of action theory, I explore the idea of the resistance of desire, as proposed by Timo Airaksinen. The second concept to investigate at this stage is intention. As in the previous case, it is plain that there are plenty of accounts of intentions and there are many roles they play in the phenomenology of action. For the purposes of this paper, we need only something that can be interpreted as an approach to PF. Such an approach can be found in the idea of stability of intention or a plan, discussed famously by Michael Bratman. According to my interpretation, these two ideas, resistance of desire and stability of intention, allow to initially understand some important aspects of PF in action theory. To get a slightly more comprehensive view – and to supplement the outcomes gained on the grounds of the analyses of these two accounts – I introduce, in the third step, the concept of plasticity which comes from the so-called praxiology proposed by Tadeusz Kotarbiński (Lvov-Warsaw School). I try to show how this concept is still feasible and how it may enrich current philosophical accounts of agential flexibility. The strategy behind this stage of the paper is to enrich the Bratmanian approach to psychological stability. The last part of the paper contains some remarks on the philosophical outcome of the interdisciplinary approach to PF. (shrink)