I believe that if you're sad, you're frustrated or angry or any type of emotions that you're feeling, it stems from something and that there is root cause to it. And the practical way that I would do is to...

I would reflect on my own and ask some questions like why do I feel this way? Why do I feel angry or? anxious or sad what's the reason behind this and I will be honest to myself

but the key here is to reflect what really is your problem what makes you so upset what makes you change your emotions so often and

You can also think of the stimulus that is affecting these changes so that you can pinpoint where exactly should you focus your whole attention to to be able to help yourself.