The assurance of the free grace of God was the experience of the early Methodists, which the Wesleys set in the Christian tradition of 'arminianism', emphasising within human freewill the need for holy living as an outcome of faith leading towards 'Christian perfection'.
The Calvinists (such as George Whitefield) by contrast stressed the absolute sovereignty of God and believed in predestination.
This implied that some people could never reach God, no matter what they did, as 'the elect' had already been chosen.
But Wesley and the Methodists preached that all can be saved. No-one is beyond the reach of God's love.