Wrestling

Sinclair Ferguson writes the following in his book Christ Alone:

"The struggles we sometimes experience in prayer, then, are often part of the process
by which God gradually brings us to ask for only what He has promised to give.  The struggle is not our wrestling to bring Him to give us what we desire, but our wrestling with His Word until we are illuminated and subdued by it, saying, 'Not my will, but Your will be done.'  Then, as Calvin again says, we learn 'not to ask for more than God allows.'"

Jacob spent his time wrestling and striving for what God has promised.  He only need to claim that promise.