It's important to celebrate a user completing an action during their journey. Success messages will let the user know that they have completed an action. These messages should leave them feeling:
Satisfied with their efforts
Reaffirm the outcome and get out of the user's way. Always give them the option to dismiss the message. If they just created something, give them the option to view it.
Keep the information useful and don't disrupt your users experience with the message
Use short sentences
Allow them to dismiss the message
Success messages that appear more frequently should be more concise and have less wink. If messages are appearing repeatedly, consider multiple versions if you want to add a wink.
Messages appearing after a bigger, optimistic action can be more playful.
The following example confirms a sign-up subscription. It’s optimistic, clear and concise with a call-to-action that encourages the user to keep going.
The confirmation flag below is a clear and practical confirmation that an action has been completed. To keep the user working, they are presented with two common actions.
This Bitbucket success message uses a lot of "wink" to encourage the user to start working.