How do I loosen a one push pull tub handle? It is too tight to pull and push.

Need more info. Model/manufacturer if possible. Sounds like you may have a Moen. Most single handle cartridges can be removed after shutting the water off to the tub/shower and opening the valve to relive pressure. If too much wear or build up inside the cartridge has occurred you may want to consider replacing the cartridge as opposed to servicing it. Silicone greases are available for lubing o-rings and moving parts of the cartridges before reinstalling. Do NOT use silicone adhesives/sealants. They are different than silicone grease.