1) How do you manage the expectations of your clients?
I find it best to have a face-to-face meeting and get the client to express what they want; if they're uncertain, I can bounce ideas off them and get a feel of what they want. This approach is especially important with wedding photography where the meeting acts as a great way to get to know the couple, take some test shots, and make them comfortable with being photographed. And once face-to-face, you can also discuss the business aspect - to negotiate the finances.
Once a brief has been reached, that gives me the scope to plan ahead so that the pressure on the day is less so.
2) How do you deal with clients who were expecting more than you could deliver?
If it does happen, then this is a good exercise from distinguishing a professional and an enthusiast. The photographic experience should be enjoyable for both parties, not just fun for the photographer.
Thankfully this hasn't happened to me for the above reasons. If you understand what the client wants and aim for that, then there's little scope to go wrong. I've heard problems from event organisers that the photographer they hired didn't live up to expectation(s) because they didn't listen to what they wanted.
3) Do you feel the pressure/have anxiety in terms of being able to deliver something meaningful and visually pleasing?
This I've grown accustomed to. The challenge on the exhibition about nothingness was one of the harder events I've covered over the last 2 years purely because of the meaning and the aesthetics. For conventional event photography, each photographer will eventually develop their own style for coverage whilst learning how to adapt; what it allows me is to follow the brief I've been given by the client, and to also get those banker shots from force of habit in case things don't turn out so well. Planning in advance also reduces the pressure load as you're more familiar with the venue and with the lighting so you can get more out of your photography.