Your cell parameters are designed considering your link budget calculations. In link budget we make appropriate changes so that losses in ul & dl are same and the difference (pathloss) is zero (for MS perception).
If you have pathloss which is either +ve or -ve (higher values, depending on the site locations) then you have path imbalance which causes problems in the link making it unstable.
Though there are some exceptions for living with high PB values.
I hope it answers your query though in a nutshell.