Two people can be "outwardly" doing the very same thing (like shmiras habris for example), and yet on the "inside", they are completely different.
1) You can be doing shmiras habris by: Running franticly from the y"h thereby feeling pressure, fear, anxiety, eventual exhaustion, which in the end can lead to a fall. Why? It is the VERY stress and anxiety of this type of approach which beckons us to return to the acting out, in order to sooth our pains - so to speak.
2) You can be doing shmiras habris by: Instead of running FROM the y"h, running TOWARDS Hashem. Your entire focus, contrary to the above, is one of GOING somewhere that I wish to be (Hashem), rather than running from a place I am frightened of. The first option produces anxiety which can feed the problem, the second, i.e running TO Hashem's palace, will produce a different type of feeling... because you are doing something completely different. You are building and strengthening yourself with each step, as opposed to "fleeing", which causes tiredness with each step.