You may be trying to slow down your pace or lack the means to make speedy progress. Walking is a dichotomous symbol in that it can be both frustrating and relaxing to walk.
Walking is much more of a discovery-oriented journey than driving, flying, or other modes of transit. When walking, you are forced to experience your environment in much more detail since you are moving through it so slowly. To walk in a dream, especially if your perceived destination is far off, may indicate that you are missing some of the pleasure life has to offer by fixating on destinations, rather than on journeys.
In order to see the interpretive value of the walking, it must be determined why walking is the preferred mode of transit.
Are there other dream characters involved in walking, marching, or hiking? Are you trying to walk in an environment that is normally traveled by car?