Be Honest with Yourself
In my opinion, the vast majority of problems people face, be it regarding relationships, career, whatever, is caused by the fact that people aren't honest with them. Sometimes it's cause of a lack of ability to be self-conscious. Sometimes the ability is there, but people are too egotistical to train their eye on themself.
I would say 99% of the problems that arise can be solved if people were simply honest regarding themselves and their situation. If people could just get over their Desire & Attachment for a moment, and look at things objectively.
That coupled with the fact that people rush into relationships before they are COMPLETE, thinking that relationships will make them complete, are the two leading causes of 99% of relationship problems in my opinion.
Most people aren't terrible. Most people are just selfish, and inconsiderate cause they think that's what is needed to "win" in this world.
Just BE. Be the best you can be. Don't look to a relationship to make you whole. Look to improving your skills. Look to going to work out (not for vanity, not for compulsion or obsession, simply to improve yourself health wise). Look to becoming more personable and social. Just BE yourself.
Do that, and then you can be honest with yourself. It's not easy to be honest when what you learn hurts. When you are honest with yourself you can understand your needs and capabilities best.
The last thing I would add is a saying I'm very fond of (patent pending on this one, its one of my favourite sayings I made up):
"Always be content, Never be Satisfied".
Meaning: Always be happy with what you have. No need to beat yourself up for what you don't have. BUT, NEVER be satisfied. Satisfied comes from the Latin word SATIS, which means FULL. So be content with that snack you ate (for example), even though it doesn't fill your stomach to the full.
This is my advice on 99% of the problems that people deal with regarding relationships.
/rant
