Why does the motor on my pool pump keep going bad?

I’ve got a Pro-Line pump & element filter for my pool & the motor got all loud shortly after I bought it. Instead of repairing it each pool supply place I contact tells me to replace it. But then within days of replacing it, it happens again like clockwork. I can’t count how many times this has happened in the last several years. What causes this, & more importantly, what can I do about this?
[I’ve tried looking for an owner’s manual but can’t find one.]
Any ideas?