The biggest obstacle is pride. Once you for the habit of receiving on the tongue, you will experience a more profound union with our Lord. Ask Him to strengthen your humility.
I've always received on the tongue, but it was out of fear of my own klutziness, rather than humility. I once almost took out a whole ciborium, tripping when curtseying down to receive from a miniature EEM (there oughta be a rule: you must be this tall to distribute the Eucharist). That was years ago & it still gives me chills. Once a priest dropped the Host he was giving me (not used to people receiving on the tongue, I guess) and it caught in the bobbles of my sweater. I picked it up & consumed it. I guess technically I wasn't supposed to do that, but better that than to have him handling my bust to retrieve it, or to let it fall all the way to the floor.