That's right having the same password for all or most of the platforms is always very risky having that password manager is one of the best possible options available right now so do you suggest any of the best such apps? or the ones do you use just might help others to save some time in searching for those or filtering some
Avoid using LastPass, 1Password or any other online tool. Use KeePass instead, it works offline and it's open source.
Write it down on paper is the safest tool.