If you just crimp on the exposed wire after you've stripped the end of it, the wire can eventually break over time and fail. It won't carry current anymore and might even short on something
However, if the wire gauge is small enough, bend the wires back over the insulation and then insert it and crimp. That way your crimping onto the wire AND the insulation and it will last MUCH longer and the wire won't fatigue.
Don't over crimp though, you'll cut through things.
Or just get some good connectors from Jim Davis that have crimps for the wire and the insulation.
