Does this resonate with you? It sounds "easy" to say look on the "bright" side but sometimes that can feel tricky.
Here are some techniques which might support you:
Separate fact from fiction (what is reality and what is emotive?)
Identify a positive (what one thing is a positive?)
Cultivate an attitude of gratitude (what one thing can you be thankful for?)
It can help to write thoughts and feelings down this can be supportive and also show you how far you have come