I think for the first "honeymoon period" you feel invincible, and you don't notice the sneaky ways that a lot of clients will use to try and get one over on you, or the disrespectful ways don't bother you as much, because you don't yet know their game . Nowadays I can read them from the minute they come in the door, or even on the phone, I can predict the behaviour to a tee, even the phrases they will use
Also the money seems never-ending and you adjust your lifestyle to fit that and all of a sudden you find yourself burnt out but with huge rent etc and a designer lifestyle.
I've been working for years and years and I find I really need to keep a check on it, or else I do get burn out quite easily. I find having the attitude of 'I will give as good a service as I can but I will not be affected by ANYTHING clients say about me - bad or good, and I will keep my feet firmly grounded in real life' helps immensely. As does a "purpose" for the money rather than just frittering it all away.
I can tell I'm in burn out when I feel a horrible anger feeling rising up at even the slightest of bad client behaviour and the thought of another client makes me feel serious dread. Also I just want to wear "non-sexy" clothes like big sweaters and not deal with men in general at all, except a very chosen few non-client men lol. I just need to take a day off or a couple of days off when that happens, regroup and refocus on my plans for the money then get back into action. I find the phone has to remain totally off for 1-2 days and all work related websites cannot be visited!