To have a heel come off while you are walking is an indication that you will have some excellent luck within a short time, particularly if the heel is not lost but is fastened on the shoe very shortly afterward.
To catch the heel in a hole or iron grating is a sign that you will be thwarted in some plan that you have made.
To dream that you wear shoes with very low heels is an indication that carelessness will be likely to cause you difficulties which you will find hard to overcome.