Betrayal is such a big, powerful word, a close relative of rejection, and something which is frequently the cause of serious emotional problems. As you might expect, I come across it a lot in clients, and like rejection, there is a reason it hurts so deeply - it's a protective process, to warn us of future incidence and prevent recurrence. It's dangerous, literally life-threatening on occasion, so the consequences are very painful.
One concern with this is that it can cause people to withdraw from forming full and rewarding relationships with others. They are forever tainted with suspicion and mistrust, unable to allow themselves to be vulnerable, hardened and cold, unwilling to let anybody close. It's a tricky balance, because nobody wants to end up being hurt all of the time, and it's fair to say that some people do consistently make disastrous mistakes in choosing friends and partners, which is a warning sign in itself (and a whole other topic!). However, if they cannot be open, they can never experience the joys of a meanngful relationship with another person.
In which case, do we have to accept betrayal as part of our existence? I think we do, it's almost inevitable. If you never experience it throughout your life, you are a lucky person indeed (or possibly deluded/devoid of feeling!); if you have experienced it, join the human race! In the aftermath, much self-examination may be required - Was it really betrayal or were expectations unrealistic? Are you over-reacting? What brought you to this? And so on. Then there are the following questions - What is it about the other person which caused them to behave this way? Can you forgive in the circumstances or is it a warning sign? What can you learn from the experience and take with you on life's journey? Easy, huh?! Don't give up - remembering it's tough for everybody may help.