Sad and I dont know why

At times I get sad and scared for no reason at all. I could of had the best day ever and yet a dark cloud comes over me. I sit here and ask myself why am I feeling sad and scared? Yet I have no answers. I start to feel unsafe and have to ask my husband to just hold me close. I hate this feeling that I cant control and have to keep telling myself that I am ok. I have a home to live in, food to eat and there is nothing that is harming me. I am perfectly fine, yet I start to wonder if everyone I know is ok, are my kids sleeping ok, are my parents health ok and is something bad going to happen tonight? Do you ever feel like all of a sudden something is not right and cant figure it out. Do you just go to bed and close your eyes? Does it affect yoyr dreams and you wake up scared? Or does it go away and wake up like you were never scared? I ground myself with simple steps but sometimes they may or may not work, I tell myself I am happy, my family and I are safe and that there is nothing that is going to happen to me because i am safe in my husbands arms. How do you deal with anxiety? I know I am not alone.