Snails crawling in your dream, signifies that unhealthful conditions surround you.
To step on them, denotes that you will come in contact with disagreeable people.
To see a snail in your dream suggests that you are being overly sensitive. You may feel shy but wish to be more outgoing and energetic.
Alternatively, it suggests that you are making steady progress toward a goal.
You just need to go at your own pace.