Be careful for nothing; but in every thing by prayer and supplication with thanksgiving let your requests be made known unto God.
"[I]n everything" we are to give thanks. We are to be thankful even in times of trials. Even when we are suffering we are to be joyful. Why? Because you can not be joyful and full of self-pity and anger at the same time.
There is always something to be grateful for in your life. Foster a life of gratitude and thanksgiving and you will have less bitterness.
I've written before about Ann Voskamp's book, One Thousand Gifts and how I journaled my 1000 gifts (here and here). I heard of another way to catalog gratitude--The ABC's of Gratitude (looking back at my blog I saw that I did an ABC's of Thanksgiving 5 years ago). Try to make a list every day (or every week) and find something to be grateful about for each letter of the alphabet.
F--Ford (my son, not the company!)
K--Kitchen (both in my house and the new summer kitchen!)
L--Long time friends
O--One flesh (Chad!)
U--Ultimate sacrifice (Christ's blood!)
X--X-tra beautiful sunsets