I will try to explain with an example. Let us say from nozzle to the spring the direction vector is in -Z and you have a vertical riser above the spring.Also let us consider that you were getting
a high -Mx.By increasing the load on the spring you were trying to counter the negative moment with a counterclokwise (+) moment and thereby reduce the resultant moment on the nozzle.

Try to visualize the free body diagram and the rationale of the solution will immediately come out.

Anindya Bhattacharya