I can't use techniques in real-life situations.

I can't use techniques in real-life situations. I learned some techniques in stuttering therapy that I know help me a lot and reduce a lot the duration of my stuttering, the technique is still awkward but if you compare it to a 5s block (or in bad days 10s), a little 1s prolongation is way better, but, my mind or body I don't know keeps resisting to use the technique in real-life situations, and keep going back to the brute force long and stupid blocks, even though the technique is the right choice. How do you overcome this thing? Why does this happen? Why do our bodies resist change even though it's better for us? Wtf bro, I can't understand.