"Trust is earned, not given." someone once said. That is a hard way to live. Unfortunately, as time goes by, it seems that more people need to live by that credo. I, for one, look at things a bit differently. I believe that everyone deserves to be given trust right off the bat. Then, as their actions dictate, you give them more or take away your trust. That doesn't mean you trust everyone completely but it does mean that everyone deserves a chance.
I once heard this exchange:
The question was asked: "If by trusting I am hurt - is it worth it?"
The answer was: "By never trusting are you not hurt even more?"
If you never trust anyone you will miss out on a LOT of wonderful experiences in life. You will also miss out on some important lessons you need. Is squandering your trust really worth that?
Building up walls and denying trust to people can isolate you and leave you feeling very lonely. Yes it IS true that any person you give any degree of your trust to can decide to take that trust and abuse it and that hurts. We all have that option. But once they do this you are aware of their nature and you can respond accordingly by reducing or eliminating the amount of trust you have invested in them.
If you never trust then you will never love nor will you know the happiness a friendship or love can really bring.