Romans 11:22 Behold therefore the goodness and severity of God: on them which fell, severity; but toward thee, goodness, if thou continue in his goodness: otherwise thou also shalt be cut off.

You can both love and fear someone. For example, especially a child may love a parent, but also be fearful of this parent, since he knows, if he does wrong, he'll be punished.

Now the word punishment is still an understatement, when we're talking about God.

The punishment isn't temporary, but may be eternal, and highly highly severe beyond belief, as Jesus stated:

Mathew 25:46 "Then they will go away to eternal punishment, but the righteous to eternal life."