Develop a "system". My ex used to laugh at me but I have had the same set of keys for my folks house for 35 years. (only lost them once). I carry them every day on my house ring.
Always, always, take the time to put important things in the same place every day. Keys on a nail or in the pants pocket. That is the ONLY place they go. Same pocket every day. Same nail every night. Once you develop the system you will actually feel weird if you don't have everything on you that you need. When you leave the house or come home.
I do that for my wallet, cell phone, multi tool, car keys and house keys. NEVER lose them.
Start out taking some time to get everything organized (use friends, family, or a professional service if needed) and from there it is really just maintainance. Make a list of what needs to stay organized, devote a small amount of time each day (or a regular time block that your schedule allows) to keep it that way, and stick to the schedule.