It's natural that due to some situations we attain hard feelings towards some people. With time, they may grow and become uncontrollable to not express. Yet, if we refrain from expressing hard feelings towards people, anyone for that matter, with time we stop having them. The resilience builds up in us. We start experiencing life as it comes and that includes those people in it with no much friction. That's the moment we know we have gained one of the most important attributes to live, BALANCE. Balancing our good and bad thoughts is equally important, especially then when it's towards any person.
Stop expressing hard feelings towards anyone.
You will stop having them in time!