They ignore you now but they'll need you later, that's life.
Sometimes people will undervalue you, it just happens in life. People are sometimes selfish creatures, and though they may not always have the worst of intentions in mind, they don't seem to see things until they need to see them. Not everyone is able to look at things with a compassionate eye, whether it be because they were never taught to do so, or that it be they choose not to think of anyone other than themselves.
You can't let another person's selfishness, lead you away from being compassionate and selfless. Not everyone will behave the way that they should. But hold still to who you are, and be an example in life to those who have trouble seeing light. When you let another persons negative ways stop you from being the person you aspire to be, you lose! Remember they may ignore you now, but if you continue to be a positive uplifting spirit, they are going to need you later.