Planting a garden takes work. Clear the ground, prepare the soil. Choose where to put which seeds. Then, nurture them. Prune when and where necessary. Harvest.
An affirmation practice is the same. You’ve got to unwind and uproot negative belief patterns, and plant positive ones to replace them. The nurturing process means you throw out what doesn’t work. Time shows rewards, as we harvest more happy days or better health or relationships.
Affirmations are nothing more than the thoughts you think and the words you say, but it’s a practice to cultivate, a garden to grow. If you doubt you can, you just haven’t gotten quiet enough to hear your inner voice clearly yet. It's a journey, sure. But one that yields great rewards.