If you talk to any of the life coaches out there or read books surrounding the topic of how to have a positive attitude or live a happier life, you will find one of the most repeated pieces of advice is to stay thankful and continually practice thankfulness.
Constantly remind yourself of things you have to be thankful for. Replace your negative thoughts with thoughts surrounding the things you are thankful for.
In Paul’s letter to the church at Thessalonica, he advises that giving thanks in all circumstances is actually the will of God in our lives (1 Thessalonians 5:18). Paul also wrote in Colossians 4:2 that we need to devote ourselves to prayer, being watchful and thankful. So it's clear that thankfulness should be an integral part of our prayer life.
Want to improve a relationship? Remind yourself why you are thankful for that person or list the things that he or she has done for you. Want to improve your outlook on your job? Be thankful that God uses your job to provide for you and your family. Want to improve your attitude towards the cold weather? Hmm...Yeah, I've got nothing for that one.
Negativity can be a default in our brains that can easily ruin our attitudes towards people, places, and things. Reflecting often on why we are thankful for everything God is doing and has done in our lives can be an effective tool in replacing that negativity with something positive.
If you want to take it one step further, write it down. Try doing it daily. Our family has a stack of 365 notecards on the kitchen table organized by day and month. One of the things we are doing this year as a family is writing down things we are thankful for each day. I would encourage you to try it as well.