learn to edit your thoughts. focus on the positive ones. ignore the negative thoughts. it's easy to fall into the trap of negative thinking and believing those thoughts. they drain us of our energy and prevent us from being fully present in the moment.
i know how easy it is to believe all the bad things that our mind tells us. "you're not good enough" "you're too fat/ugly/stupid" "you'll never be able to do it" believing those thoughts brings depression, and a crushing feeling of hopelessness. i've been there. i've also managed to come out the other side. i taught myself to focus on the positive, to ignore that little 'voice' inside my head telling me that i wasn't good enough.
smile - seriously, just smile. it will instantly lift your mood and make you feel happier
focus on the positive - teach yourself to only think positive thoughts.
surround yourself with positivity - find some quotes, or make your own, write them on post-it's and put them on your mirror, by your bed, in your purse, by the computer - any place that you'll see them throughout the day.
take action - all those things your mind tells you that you can't do? just do them. try one - and when you've done it, you can tell that negative thought where to get off
give thanks - keep a gratitude journal, every night write down five things that made you happy that day. if you're feeling hopeless, read back through it and see how blessed you are
let go of perfection - no one is perfect, and it'd be pretty dull if we were. accept your mistakes and move on.