Sounds like you are pressing too hard on the spike. If you are sitting down when using it, it could be you have it too close to you, push it away from you a little. Also the blade should be facing you - and try turning the card or paper rather than the cutter this will avoid you getting a large hole. Always use a cutting mat.
Best thing is to practice on scrap bits of card or paper, you will soon get the hang of it.

Hope this helps.
Adele x