Stalking happens to be one of my specialty areas. In fact, some of the content in the USDOJ's training manual on the topic came from yours truely.
Yes, there's the possibility of psychological damage. Case in point, British singer Adam Ant who had to be hospitalized for depression/nervous breakdown after an extended stalking spell. However, in order to bother with a law suit over such damages, you'll really need a licensed clinician who can stand before the court, testify that they've been providing treatment and/or counseling or other services, itemize symptoms leading to a diagnosis, provide a prognosis or anticipated level of possible recovery etc. before a dollar amount for damages can be evaluated. In other words, if it hasn't been SO psychologically damaging as to cause you to seek help, it's not likely to be fruitful in court. (Again, I'm not saying I agree with this situation, only that it is what it is - anyone can stand up and say "oh God, I'm scarred for life. It'll take more than that, like outside evaluation from a neutral third party, to establish.)
Psychological damage suits where the primary method of harassment is veiled, as opposed to flagrant or at least concrete threats, almost always go nowhere. Particularly when the medium is at least mostly electronic and it's just as easy to delete an email without reading it or to delete it once one can ascertain the nature of its contents. (Again, not that this is morally, or ethically correct, but if you want to see a jury roll their eyes in unision, try to explain why you're damaged by emails that you continued to willingly read.) You might get SOME level of punative damages for harassment if you can show a pattern of behavior, but damages for psychological injury in this case are going to crash almost from the start. If you decide to try to sue, get an attorney willing to work on contingency (if you can't find one willing to wait to get paid until you win, that's a good sign that even your attorney doesn't think a win will happen - if they make you pay up front, they'll get their money even if you walk away empty handed).
Yes, stalking and harassment cases are often linked to homicide cases, but the realistic truth is that such cases almost always have elements (usually several) not included in this particular case; no children together, no prior sexual or emotional relationship, never owned a business together, the person has never previously assaulted you, no concrete threats, or any of the other numerous items that would normally be even mid-level warning flags or indications that any escalation would be expected. There's also no dynamic where the person in question WANTS something from you. Most stalking cases that end up escalated center around something the stalker WANTS. Wants a relationship. Wants you to stop sleeping with his wife. Wants you to say, or do, or think something, or wants you to behave in a certain way. People don't stalk because they're bored - they do it as a means to an end. Before you try taking this before a court, ask yourself this (because the defense will certianly ask it): what does this person WANT? What have they asked for, threatened you about, what is their course of action trying to get you to DO? If you can't come up with something firm, the defense will have an easy win with one sentence "so, ladies and gentlemen of the jury, my client readily admits to being a jerk, and he's too stupid to realize that he shouldn't have continued to communicate with this plaintiff, but there's no INTENT here". (This intent being different than criminal intent, in which the end desired product is fear...the civil case will want MORE than that....fear WHY?)
As in all things, the criminal side of the equation will work a little differently - somewhat more in your favor in this case, so if you've got the evidence to substantiate the harassment, then go file for your restraining order. You don't need an attorney to do this.
If you'd like some professional level references on offender assessment and assessing dangerousness, I'll be happy to provide.

