Is my non-compete clause actually enforceable or can i ignore it

So i just got hired at a new company and they want me to sign a non-compete agreement. i am worried because i have been in this industry for years and i have a lot of contacts. If i leave this job in like two years, would they actually be able to stop me from working somewhere else in the same field? What makes one of these things enforceable or not. i need to know if this is something i should really be concerned about.