Here are a few pieces of life advice that I've tried to live my life by:
If you blame it on someone else, don’t expect it to get better. -- You're the one responsible for 99% of your problems, and you're the only one who can fix it. It doesn't matter if it's health issues, interpersonal problems, or lack of motivation--it's YOUR life, so it's time for YOU to deal with the problem.
“There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self.” -- I love this Ernest Hemingway quote! It's easy to feel that you are better than your friend, your girlfriend's ex, or your father/mother-in-law, but it's not a competition to be better than anyone else. The only person you are in competition with is yourself. The only way to make progress is to be "better" than the person you were yesterday, last week, and last year.
Have the courage to live a life true to yourself, not the life others expect of you. -- This is always easier said than done! We all have a lot of things we believe we "should" do, say, and be. If we live life according to those "should's", chances are we'll strive for a pretty impossible-to-achieve standard. To life a truly fulfilling life, you need to determine what matters to you, and strive for THOSE things. Everything else is fluff.
Only pack what you can carry yourself. -- I like to think this means "handle your own shit". If you have problems, deal with it yourself. If you want to take on a new project or challenge, make sure you are able to handle it. You'll always have people to support you, but you shouldn't bite off more than you can realistically chew.
Don’t give up what you want most for what you want now. -- This is one I cling to when I'm sitting at my desk hammering away at a keyboard while all of my friends are out partying, or when I'm drinking a cup of water instead of having a beer. There are a lot of things I really want in life, and as tough as it may be, I'm okay to give up on a lot of the "right now" things if it means I eventually get the "want most" things.
Try not to take anything personally. No one thinks about you as much as you do. -- Nowhere else in life is this as true as with children. My kids are always doing things that drive me nuts, but they're not doing it to disrespect or disobey ME--they're just doing it because they want to. If I take it personally, it can be blown out of proportion. But I'm not even in the equation! When I remember that, it's easier to manage the situation objectively.