First off, I'm so terribly sorry for the loss of your Mom, and the terrible feelings that follow. I am all too aware of the sadness you feel, and sympathize with you completely.

Hawaii - the symbolization here is reliant on your feelings for this place. How does being there make you feel, what does it represent for you? Tropical, rest, peacefulness, the need for a vacation...etc.

Black person - depends on your own skin color. If you are white, a black person would represent your natural drives, urges, longings, and emotions uncluttered by intricate social taboos; your own feelings about black people (or if the person is known or reminds you of someone specific, what you feel about him/her); your own unexpressed or repressed 'self'; a 'shadow' figure depicting a depressed or unaccepted aspect of yourself; feeling downtrodden.
If you are black, the black person representation would be as with any other 'person' dream.

Horse - represents strong, physical energy, free spirit, and pleasurable exuberance (the sort of enthusiasm or feelings of well-being that can 'carry' you through the day easily), dynamic sexual drive, the physical energy and life processes that 'carry' us around.
The horse also depicts human instincts that have been harnessed, or socialized for generations, but have been let fall into non-use. It is also a survival drive, love, all yearning toward service, toward metamorphosis, all that has powerful energy to move us.

Black or dark horse - signifies mystery, wildness, and the unknown. You may be taking a chance or gamble at some unknown area.

White horse - then it signifies purity, prosperity and good fortunes.

Riding a horse - freedom, a need to feel empowered, balance, and your possible need to tame the wild forces within yourself.

Hurry - suggests that you feel you may be unprepared in a current situation, or that there is a lack in your planning of things.
Alternatively, you may be feeling out of place. This dream may also be a literal reflection of your daily life where you feel that you are always in a rush, or overstressed, and that there is not enough time to do all the things you want to do.

White buffalo:
White - White is feminine. Symbolizing virginity, but also emotional coldness and immaturity. Also, purity, well earned success, honesty, virtue, innocence, peace, happiness, joy, transformation, cleanliness, dignity, awareness, clarity of mind, and light feelings. White in a dream might possibly be a reminder to resolve special situations and problems.

Buffalo - represents power, resolution, and survival. May refer those human animal aspects that survive through difficult situations. May represent fertile opportunities that are offered to you in your path to self awareness.

Herd of buffalo - signifies tranquillity, protection, and plenitude.

Charging buffalo may be a warning from the subconscious that you are going off your life path, and that you need to stay on course.

Woods/Forest - represent the aspects in the subconscious; growth and strength. Also solitude, quiet, and an affinity for nature and natural things.

Hide/Hiding - suggests the unwillingness to face something, or situation in your waking life. In daily life we hide from things that we don't want to deal with or we hide from danger. If you are hiding out of danger, then you should consider those things in your life that you feel propose a threat to you. They could be internal forces or environmental conditions. Generally, we attempt to hide our own negativity and mistakes. This dream may call for an honest reflection on personal characteristics and an evaluation of how much fear influences our lives and decision-making.

Leaves - represent the living, growing part of you. The part that is still vulnerable because of it's newness, or outworn(depending on the color of the leaves) part of your thinking or feeling.
You can also be 'blown like a leaf', suggesting separation from your roots or main growth; or you can take 'a leaf' from sombody's notebook, thus following their example or idea.

Water - represents your subconscious, your emotions, and your accumulated life experiences, and the flow of 'feeling' energy. It is also a symbol of new life, refreshment, vigor, energy, cleansing, emotional stirrings, fertility, growth, and creative potential.

White wolves: (see white symbolization above)
Wolves - Wolves may have positive or negative meaning and may represent good or evil in dreams. They could represent hostility, aggression, sneakiness, and ferocious appetites. In some cultures, wolves represent feminine energies and in others masculine. In the Native American culture and tradition, the wolf is a symbol of a mysterious and wonderful teacher. Wolves are considered to be powerful guides who offer wisdom and enlightenment.
A wolf may also symbolize all that you are afraid of in yourself, particularly what you see as "animal", aggressive and destructive. Probably your fear is irrational and stems from a traumatic childhood experience.

Cow - signifies your obedience to authority without question. It symbolizes your passive and docile nature. Also, often symbolizes your mother, or motherhood, in the way a mother cow protects and gives an abundant supply of milk {nurturing}, and therefore, represents maternal instincts or the desire to be cared for.

For a man - They also represent the animus or feminine aspect of the male psyche. To realize this aspect {feminine} and incorporate it into your life, gives balance to your life.
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This type of anxiety dream is probably stemming from your depression, and grief, surrounding the recent passing of your Mom.  Your subconscious may be telling you that you have the power to overcome your depression and grief. That you should allow it to be memories of the happiness and love you felt, rather than dwelling on the negative.

I hope this give you some insight, and hope.
Hugs,
J