There are many reasons why babies cry, some examples are: hunger, needs to burp, dirty diaper, tired, wants attention (or to be held), too hot or cold, something is hurting the baby, teething, stomach problems, not feeling well.
But every time a baby cries there are different ways you can comfort or soothe the child, such as: change their diaper, feed them, rock or just hold them, play with them, and check the tempature of the room.
When your child is upset this may cause you to become overwhelmed or panic but there are ways you can calm yourself, such as: exercise, take a nap, do some form of yoga, just spend some quiet time alone, try to slow your breathing and relax.
There are also other people that can help you so don't feel like you are all alone. You can ask for help from: family members, experienced parents, M.O.Ps (mother's of preschoolers), your neighbors, or a doctor.