In general, unsolicited advice is not advised. It is telling someone that you know what is better for them than they themselves do.
I have an acquaintance who barely knows me, is considerably younger, not exactly the picture of success himself, who likes to tell me what I should be doing with my life. Like - shouldn't you know me before you tell me what is good for me? And don't you think that at my age I have an idea of what is right for me? I mean, I have spent many many deep, intimate moments with myself and the only person who REALLY knows me is .... me:-)! Everybody else just gets a glimpse. Appreciate that.
Also, don't think that you are an expert on getting married b/c you are married. It is just a gift from Hashem - not b/c of your unique talents. And just b/c he/she is not married doesn't mean that they are immature and/or don't know how to have a healthy relationship. Or that they don't REALLY want to get married - b/c if they did they would of course be married.
Also don't think [and you probably don't] that you are a better human being than a single person b/c someone wanted to marry you and this person is still single. I have known many many single people who were/are much better people than I am.
Also, if people would give 1/100 of the thought, effort and tfillos into the shidduchim of others than they did for themselves - there would be a lot more married people. So think, make suggestions and FOLLOW THROUGH. Unlike so many who say "I have someone for you" - and then the single person never hears from them again [or a month later...].
