If your friend is really down in the dumps, worried about how their arrest will impact the rest of their life, have a talk with them. Make them think otherwise. It will probably be hard for your friend to wrap their head around the idea that this is not the end of the world right now. However, in time they will see that you are right. Their arrest is a big obstacle to get around, but it is possible to do so.
Tell your friend that all kinds of people have been arrested at some point in their life. If you are speaking from experience, talk about that and how you are no longer dwelling on that darker past. If you do not personally know anyone else who has been in this situation, then talk about the possibility of your loved one knowing someone who may have once been arrested. Whether it is a friend, family member, coworker, bus driver, or the guy they see at the gym all the time, there could very well be someone they know who was once arrested.
Have your friend really think about the people they know personally. These people are successful, happy, and seem to lead normal lives. No one could tell if these people had a brush with the law once.
Now picture your friend in just a few years. People will look at your friend the same way, never guessing they had been put into handcuffs at one point in their life. Your friend will not be denied from getting a job, moving into a new home, or getting a loan all because of one arrest record. Your friend will be truly happy again. Sooner or later, they will forget the troubles they are going through because of one mistake. This arrest will not dictate how they live the rest of their life. Only they can do that.