There are two jobs that I lost under frustrating circumstances.
The first was typical. I bid on a job, someone sent me a private message asking me how quickly I could finish and then awarded the job to someone else before I got back to them. These are the most frustrating jobs, because (1) Guru's messaging system is quirky and (2) my response times are usually within the hour, but I do occasionally sleep and work on other projects. To lose a job simply because I received the message at 9:00 PM and did not respond until 7:00AM has me kicking myself. Usually, I am available until midnight.
The second is even more frustrating. Many times I have received messages that say something like, "Wow, I really like your profile, and your price is fine, but I am going with someone else on this." Grrr. Why? Why me? I did nothing wrong and I still didn't get the job. Sigh. The story of my luck.
I suppose I am happy the person contacted me - he said he hoped we could work together on a future project. The bad thing is that he closed the conversation, so I can't even respond. I also, don't necessarily believe he will choose me.
I once had a guy who kept sending me invitations to his projects, but when I applied he would never choose me. Why? I have no clue. Once I have applied a certain number of times to the same employer, I eventually mark them on my "do not apply" list and stop wasting my time. I am flattered you want to use me, but really I want to be chosen, not flattered.