Questions need to be answered

1. Can someone define, what it means to have a lust on someone, to like someone and to fall in love with someone?

2. Say if a person is so happen to like one of his colleagues who is suspected to be in relationship, should he tell her, or should not, fearing for rejection? And of course, spoiling the current friendship.

3. Is it true that opportunity in getting into a relationship is one time only? Does that mean, if we screw up the first one..we'll be fucked up for the rest of the life in getting involved with the same person again?

Can anyone who is either experienced or wise to answer these questions. Thank you very much.