For me it is a convenient and compact tool in which I can put all my ideas, goals, thoughts
Evernote - Bring your life's work together in one digital workspace. Evernote is the place to collect inspirational ideas, write meaningful words, and move your important projects forward.
Google Keep - Capture notes, share them with others, and access them from your computer, phone or tablet. Free with a Google account.
Laverna - Laverna is a JavaScript note taking application with Markdown editor and encryption support.
Joplin - Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. The notes are searchable, tagged and modified either from the applications directly or from your own text editor.
RedNotebook - RedNotebook is a software that format, tag and search entries and add pictures, links and customizable templates, spell check notes, and export to plain text, HTML, Latex or PDF.
Simplenote - The simplest way to keep notes. Light, clean, and free. Simplenote is now available for iOS, Android, Mac, and the web.