Newbie, texas rig, failing to set hook

I'm not particularly experienced at fishing, and have just started fishing
texas-rigged plastic worms. I get lots of good bites this way, but never
manage to set the hook. I've switched to wide worm hooks to no avail.

I know the fish isn't spitting out the bait, because if I open the reel, the
fish will swim away with it until I try to set it (and proceed to yank it
out of the fish).

Any suggestions?

Thanks,
Rick