Is it OK to leave VPN on all the time?

I'm curious about the implications of leaving a VPN on all the time. Can you explain if it's SAFE and what potential drawbacks there might be? I've heard it can affect internet speed and potentially compromise security, but I'm not sure how much truth there is to that. Additionally, is it necessary to keep it on constantly, or are there certain situations where it's more beneficial to use a VPN?