"as a single footstep will not make a path on the earth, so a single thought will not make a pathway in the mind. to make a deep physical path, we walk again and again. to make a deep mental path, we must think over and over the kind of thoughts we wish to dominate our lives."
what does this mean to you?

I think that this means that you have to keep doing/working toward the goal you have, you can't just try to do it once and quit. For example, you wish to become more positive, so you resolve to repeat in your head a positive quote when you are having a hard time, (mental),  but when the negative time comes around you do not repeat the phrase.  That means that will not make a difference So you have to keep doing it.

Hope this helps. :)