If your attitude was sad in the dream, perhaps you need to reconsider your attitude towards that person and what they represent to you. For example, ask yourself if you need to be more polite, kind or unselfish if these are the qualities you associate with the person.
If the vision was of your own grave, this suggests problems you need to dig your way out of; if a grave is neglected, this is a reminder from your subconscious not to take your health or the good things in your life for granted.
If the tombstone was of someone you knew or loved who has died, you may also simply be experiencing a sense of nostalgia for those happy days when you could pay them a real-life visit. If, however, the person is not dead, this could be a warning that your relationship is in danger of dying unless you concentrate on keeping it alive in real life.
If a vault appears in your dream, this suggests a more tentative approach to change; in older cemeteries it is possible to peer into family vaults to see the coffins, so perhaps you are aware of the need for change but are not yet able to make a clean break with the past.
If you had to visit a mortuary in your dream, is this a sign that you do not want to let go of the past? Do lingering feelings of guilt or regret remain? Or has the past caught up with you? If you dream of your own coat of arms and can see it on a tomb or monument, this reflects a desire to rise above a perceived station and to be accepted by those you incorrectly assume to be your superiors. A common nightmare is to dream of being buried alive. This may be a symbol of guilt or it may suggest a need to move away from a bad influence that is threatening to overwhelm you.
See also: NIGHTMARES [1]